Ratio
The ratio helper keeps a box at a fixed aspect ratio whatever its width, which is perfect for media placeholders, thumbnails, galleries and banners. Pick ratio-1x1, ratio-4x3, ratio-16x9 or ratio-21x9, or set any ratio with the --ui-aspect-ratio variable.
1The four built-in ratios
ratio-1x1, ratio-4x3, ratio-16x9 and ratio-21x9 next to each other, filled with a plain div.
1:1
4:3
16:9
21:9
<div class="row g-3">
<div class="col-6 col-md-3">
<div class="ratio ratio-1x1">
<div class="d-flex align-items-center justify-content-center bg-primary-subtle text-primary-emphasis border border-primary-subtle rounded fw-semibold">
1:1
</div>
</div>
</div>
<div class="col-6 col-md-3">
<div class="ratio ratio-4x3">
<div class="d-flex align-items-center justify-content-center bg-primary-subtle text-primary-emphasis border border-primary-subtle rounded fw-semibold">
4:3
</div>
</div>
</div>
<div class="col-6 col-md-3">
<div class="ratio ratio-16x9">
<div class="d-flex align-items-center justify-content-center bg-primary-subtle text-primary-emphasis border border-primary-subtle rounded fw-semibold">
16:9
</div>
</div>
</div>
<div class="col-6 col-md-3">
<div class="ratio ratio-21x9">
<div class="d-flex align-items-center justify-content-center bg-primary-subtle text-primary-emphasis border border-primary-subtle rounded fw-semibold">
21:9
</div>
</div>
</div>
</div>2Video placeholder
A 16:9 poster image with a centred play button, ready for a video player of your choice.
<div class="ratio ratio-16x9 rounded overflow-hidden" style="max-width:36rem">
<div>
<img src="https://images.unsplash.com/photo-1758270705518-b61b40527e76?auto=format&fit=crop&w=1600&h=700&q=70" alt="Video poster" class="w-100 h-100 object-fit-cover">
<button type="button" class="btn btn-light rounded-circle position-absolute top-50 start-50 translate-middle shadow" aria-label="Play video"><i class="bi bi-play-fill" aria-hidden="true"></i></button>
</div>
</div>3Square product thumbnails
ratio-1x1 with object-fit-cover gives every product the same tile, whatever the photo size.
UX fundamentals
Web development
Brand design
Project management
Public speaking
Video editing
<div class="row g-2">
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-1.svg" alt="UX fundamentals" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">UX fundamentals</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-3.svg" alt="Web development" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Web development</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-8.svg" alt="Brand design" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Brand design</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-6.svg" alt="Project management" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Project management</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-4.svg" alt="Public speaking" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Public speaking</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-12.svg" alt="Video editing" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Video editing</p>
</div>
</div>4Cinematic hero banner
ratio-21x9 for a wide banner with a headline overlay.
Short courses, real results
The mobile app downloads lessons, so you can learn on the train.
<div class="ratio ratio-21x9 rounded-3 overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1565598611425-45b0878bdd0b?auto=format&fit=crop&w=1600&h=700&q=70" alt="" class="w-100 h-100 object-fit-cover">
<div class="position-absolute bottom-0 start-0 p-3 p-md-4 text-white" style="background:rgba(0,0,0,.45)">
<h3 class="h4 mb-1">Short courses, real results</h3>
<p class="small mb-0 d-none d-sm-block">The mobile app downloads lessons, so you can learn on the train.</p>
</div>
</div>
</div>5Map placeholder
A 4:3 box reserved for a map, showing the address until the map loads.
Musean411 Orchard Close, Edinburgh
<div class="ratio ratio-4x3" style="max-width:24rem">
<div class="d-flex flex-column align-items-center justify-content-center bg-body-tertiary border rounded text-center p-3">
<span class="fs-1 text-primary"><i class="bi bi-geo-alt-fill" aria-hidden="true"></i></span><strong>Musean</strong><span class="small text-body-secondary">411 Orchard Close, Edinburgh</span>
</div>
</div>6Custom 3:2 photo
Any ratio works with the --ui-aspect-ratio variable: 2 / 3 = 66.67% for classic photo prints.
<figure class="mb-0" style="max-width:28rem">
<div class="ratio rounded overflow-hidden" style="--ui-aspect-ratio:66.67%">
<img src="https://images.unsplash.com/photo-1565598621680-94ac0c22b148?auto=format&fit=crop&w=1200&h=800&q=70" alt="Tips for learning while working full time" class="object-fit-cover">
</div>
<figcaption class="small text-body-secondary mt-1">3:2 · A beginner's guide to getting started</figcaption>
</figure>7Portrait team cards
A 3:4 portrait ratio (133.33%) for team photos in cards.
Nora Ashford
Sales Executive
Mateo Brennan
Data Analyst
Mia Nguyen
Marketing Lead
<div class="row g-3">
<div class="col-6 col-md-4">
<div class="card h-100">
<div class="ratio card-img-top overflow-hidden" style="--ui-aspect-ratio:133.33%">
<img src="https://images.unsplash.com/photo-1620829813573-7c9e1877706f?auto=format&fit=crop&w=1200&h=800&q=70" alt="Nora Ashford" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Nora Ashford</h3>
<p class="small text-body-secondary mb-0">Sales Executive</p>
</div>
</div>
</div>
<div class="col-6 col-md-4">
<div class="card h-100">
<div class="ratio card-img-top overflow-hidden" style="--ui-aspect-ratio:133.33%">
<img src="https://images.unsplash.com/photo-1523240795612-9a054b0db644?auto=format&fit=crop&w=1200&h=800&q=70" alt="Mateo Brennan" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Mateo Brennan</h3>
<p class="small text-body-secondary mb-0">Data Analyst</p>
</div>
</div>
</div>
<div class="col-6 col-md-4">
<div class="card h-100">
<div class="ratio card-img-top overflow-hidden" style="--ui-aspect-ratio:133.33%">
<img src="https://images.unsplash.com/photo-1516321497487-e288fb19713f?auto=format&fit=crop&w=1200&h=800&q=70" alt="Mia Nguyen" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Mia Nguyen</h3>
<p class="small text-body-secondary mb-0">Marketing Lead</p>
</div>
</div>
</div>
</div>8Vertical stories
A 9:16 ratio (177.78%) for phone sized stories or short clips in a scrolling row.
Elena
Kai
Nadia
Hana<div class="d-flex gap-2 overflow-auto pb-1">
<div class="flex-shrink-0" style="width:7rem">
<div class="ratio rounded-3 overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="https://images.unsplash.com/photo-1543269865-0a740d43b90c?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Elena Quinn" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Elena</span>
</div>
</div>
</div>
<div class="flex-shrink-0" style="width:7rem">
<div class="ratio rounded-3 overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="https://images.unsplash.com/photo-1565598611425-45b0878bdd0b?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Kai Harlow" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Kai</span>
</div>
</div>
</div>
<div class="flex-shrink-0" style="width:7rem">
<div class="ratio rounded-3 overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="https://images.unsplash.com/photo-1596247290824-e9f12b8c574f?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Nadia Lindqvist" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Nadia</span>
</div>
</div>
</div>
<div class="flex-shrink-0" style="width:7rem">
<div class="ratio rounded-3 overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="https://images.unsplash.com/photo-1525130413817-d45c1d127c42?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Hana Duarte" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Hana</span>
</div>
</div>
</div>
</div>9Chart area
A 16:9 box that keeps a simple bar chart in proportion on every screen.
Monthly bookings
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
<div class="card" style="max-width:36rem">
<div class="card-header small fw-semibold">
Monthly bookings
</div>
<div class="card-body">
<div class="ratio ratio-16x9">
<div class="d-flex align-items-end gap-2" role="img" aria-label="Bar chart of monthly bookings">
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:36%">
</div>
<span class="small text-body-secondary">Jan</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:64%">
</div>
<span class="small text-body-secondary">Feb</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:88%">
</div>
<span class="small text-body-secondary">Mar</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:36%">
</div>
<span class="small text-body-secondary">Apr</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:50%">
</div>
<span class="small text-body-secondary">May</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:51%">
</div>
<span class="small text-body-secondary">Jun</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:22%">
</div>
<span class="small text-body-secondary">Jul</span>
</div>
<div class="flex-fill d-flex flex-column justify-content-end align-items-center h-100">
<div class="w-100 bg-primary rounded-top" style="height:74%">
</div>
<span class="small text-body-secondary">Aug</span>
</div>
</div>
</div>
</div>
</div>10Blog card cover
ratio-16x9 as a card image keeps every post card in a grid the same height.
design
The small habits that make a big difference
Apr 21, 2026
<div class="card" style="max-width:22rem">
<div class="ratio ratio-16x9 card-img-top overflow-hidden">
<img src="https://images.unsplash.com/photo-1565598611425-45b0878bdd0b?auto=format&fit=crop&w=1200&h=800&q=70" alt="How to stay motivated when learning online" class="object-fit-cover">
</div>
<div class="card-body">
<span class="badge text-bg-light border mb-2">design</span>
<h3 class="h6">The small habits that make a big difference</h3>
<p class="small text-body-secondary mb-0">Apr 21, 2026</p>
</div>
</div>11Caption over a gradient
A 4:3 image with a gradient overlay so white caption text stays readable.
SingaporeOnline courses
<div class="ratio ratio-4x3 rounded-3 overflow-hidden" style="max-width:24rem">
<div>
<img src="https://images.unsplash.com/photo-1525130413817-d45c1d127c42?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-100 h-100 object-fit-cover">
<div class="position-absolute bottom-0 w-100 p-3 text-white" style="background:linear-gradient(transparent,rgba(0,0,0,.7))">
<strong class="d-block">Singapore</strong><span class="small">Online courses</span>
</div>
</div>
</div>12Mixed ratio gallery
Combining 1:1, 4:3 and 16:9 tiles in one responsive grid.
<div class="row g-2">
<div class="col-md-6">
<div class="ratio ratio-4x3 rounded overflow-hidden">
<img src="https://images.unsplash.com/photo-1516321497487-e288fb19713f?auto=format&fit=crop&w=1200&h=800&q=70" alt="Gallery photo 1" class="object-fit-cover">
</div>
</div>
<div class="col-md-6">
<div class="row g-2">
<div class="col-6">
<div class="ratio ratio-1x1 rounded overflow-hidden">
<img src="https://images.unsplash.com/photo-1620829813573-7c9e1877706f?auto=format&fit=crop&w=800&h=800&q=70" alt="Gallery photo 2" class="object-fit-cover">
</div>
</div>
<div class="col-6">
<div class="ratio ratio-1x1 rounded overflow-hidden">
<img src="https://images.unsplash.com/photo-1752650736024-d6aac18abc2d?auto=format&fit=crop&w=800&h=800&q=70" alt="Gallery photo 3" class="object-fit-cover">
</div>
</div>
<div class="col-12">
<div class="ratio ratio-21x9 rounded overflow-hidden">
<img src="https://images.unsplash.com/photo-1525130413817-d45c1d127c42?auto=format&fit=crop&w=1600&h=700&q=70" alt="Gallery photo 4" class="object-fit-cover">
</div>
</div>
</div>
</div>
</div>13Thumbnails in table cells
A small ratio-1x1 box keeps order line images square inside a table.
| Image | Item | Price |
|---|---|---|
| Web development | $271.00 |
| UX fundamentals | $135.99 |
| Public speaking | $81.00 |
<table class="table align-middle mb-0">
<thead>
<tr>
<th scope="col"><span class="visually-hidden">Image</span></th>
<th scope="col">Item</th>
<th scope="col" class="text-end">Price</th>
</tr>
</thead>
<tbody>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-3.svg" alt="Web development" class="object-fit-cover"></div></td>
<td class="align-middle">Web development</td>
<td class="align-middle text-end">$271.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-1.svg" alt="UX fundamentals" class="object-fit-cover"></div></td>
<td class="align-middle">UX fundamentals</td>
<td class="align-middle text-end">$135.99</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-4.svg" alt="Public speaking" class="object-fit-cover"></div></td>
<td class="align-middle">Public speaking</td>
<td class="align-middle text-end">$81.00</td>
</tr>
</tbody>
</table>14Empty cover placeholder
A dashed 4:3 area that reserves space for an image that has not been chosen yet.
No cover image yet
<div class="ratio ratio-4x3" style="max-width:20rem">
<div class="d-flex flex-column align-items-center justify-content-center border border-2 border-secondary-subtle rounded-3 text-body-secondary wt-border-dashed">
<span class="fs-2"><i class="bi bi-image-fill" aria-hidden="true"></i></span><span class="small">No cover image yet</span>
</div>
</div>15Colour swatches
Empty square ratios make perfect colour swatches for a style guide.
primary
primary
secondary
secondary
success
success
info
info
warning
warning
danger
danger
<div class="row g-2">
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-3 bg-primary">
<span class="visually-hidden">primary</span>
</div>
<p class="small text-center mt-1 mb-0">primary</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-3 bg-secondary">
<span class="visually-hidden">secondary</span>
</div>
<p class="small text-center mt-1 mb-0">secondary</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-3 bg-success">
<span class="visually-hidden">success</span>
</div>
<p class="small text-center mt-1 mb-0">success</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-3 bg-info">
<span class="visually-hidden">info</span>
</div>
<p class="small text-center mt-1 mb-0">info</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-3 bg-warning">
<span class="visually-hidden">warning</span>
</div>
<p class="small text-center mt-1 mb-0">warning</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-3 bg-danger">
<span class="visually-hidden">danger</span>
</div>
<p class="small text-center mt-1 mb-0">danger</p>
</div>
</div>16Video thumbnails with badges
Duration and status badges positioned over 16:9 thumbnails.
5:55NewHow to learn a new skill in 30 days
7:48Our favourite tips for busy weeks
9:31How to choose the right course
<div class="row g-3">
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1523240795612-9a054b0db644?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 end-0 m-2 badge text-bg-dark">5:55</span><span class="position-absolute top-0 start-0 m-2 badge text-bg-danger">New</span>
</div>
</div>
<p class="small fw-semibold mt-1 mb-0">How to learn a new skill in 30 days</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1758270705518-b61b40527e76?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 end-0 m-2 badge text-bg-dark">7:48</span>
</div>
</div>
<p class="small fw-semibold mt-1 mb-0">Our favourite tips for busy weeks</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1543269865-0a740d43b90c?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 end-0 m-2 badge text-bg-dark">9:31</span>
</div>
</div>
<p class="small fw-semibold mt-1 mb-0">How to choose the right course</p>
</div>
</div>17Media list
Fixed width 4:3 thumbnails beside article titles in a reading list.
What our students asked us most
Oct 27, 2025 · 12 min read
Five things we learned this year
Mar 30, 2026 · 12 min read
From teacher to UX designer: a career story
Oct 4, 2026 · 9 min read
<ul class="list-unstyled mb-0 vstack gap-3">
<li class="d-flex gap-3"><div class="flex-shrink-0" style="width:6rem"><div class="ratio ratio-4x3 rounded overflow-hidden"><img src="https://images.unsplash.com/photo-1596247290824-e9f12b8c574f?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">What our students asked us most</h3><p class="small text-body-secondary mb-0">Oct 27, 2025 · 12 min read</p></div></li>
<li class="d-flex gap-3"><div class="flex-shrink-0" style="width:6rem"><div class="ratio ratio-4x3 rounded overflow-hidden"><img src="https://images.unsplash.com/photo-1525130413817-d45c1d127c42?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">Five things we learned this year</h3><p class="small text-body-secondary mb-0">Mar 30, 2026 · 12 min read</p></div></li>
<li class="d-flex gap-3"><div class="flex-shrink-0" style="width:6rem"><div class="ratio ratio-4x3 rounded overflow-hidden"><img src="https://images.unsplash.com/photo-1620829813573-7c9e1877706f?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">From teacher to UX designer: a career story</h3><p class="small text-body-secondary mb-0">Oct 4, 2026 · 9 min read</p></div></li>
</ul>18Responsive ratio
A small custom class changes --ui-aspect-ratio per breakpoint: square on phones, 21:9 on tablets and up.
<div class="ratio hp-ratio-resp rounded-3 overflow-hidden">
<img src="https://images.unsplash.com/photo-1752650736024-d6aac18abc2d?auto=format&fit=crop&w=1600&h=700&q=70" alt="The online school for busy people" class="object-fit-cover">
</div>19Round avatars
ratio-1x1 with rounded-circle keeps profile pictures perfectly round even when the source is not square.
<div class="d-flex flex-wrap gap-3">
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-circle overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-1.svg" alt="Sofia Varga" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Sofia</span>
</div>
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-circle overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-10.svg" alt="Lucas Whitaker" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Lucas</span>
</div>
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-circle overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-3.svg" alt="Maya Rossi" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Maya</span>
</div>
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-circle overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-9.svg" alt="Ruby Haddad" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Ruby</span>
</div>
</div>20Loading skeleton
A 16:9 placeholder block with placeholder-glow while the real image and text load.
The skeleton reserves the exact space, so the page does not jump when content arrives.
<div class="card" style="max-width:22rem" aria-hidden="true">
<div class="ratio ratio-16x9 placeholder-glow">
<span class="placeholder"></span>
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<div class="card-body placeholder-glow">
<span class="placeholder col-7 mb-2"></span><span class="placeholder col-4"></span>
</div>
</div>
<p class="small text-body-secondary mt-2 mb-0">The skeleton reserves the exact space, so the page does not jump when content arrives.</p>