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="../assets/img/wide-2.svg" 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.
Storage pack
Business plan
Enterprise suite
Automation pack
Onboarding workshop
Starter plan
<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-12.svg" alt="Storage pack" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Storage pack</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="Business plan" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Business plan</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="Enterprise suite" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Enterprise suite</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="Automation pack" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Automation pack</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="Onboarding workshop" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Onboarding workshop</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-1.svg" alt="Starter plan" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Starter plan</p>
</div>
</div>4Cinematic hero banner
ratio-21x9 for a wide banner with a headline overlay.
From idea to release, without the chaos
Automations take care of the repetitive steps, so people can focus on real work.
<div class="ratio ratio-21x9 rounded-3 overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1690264351371-b75a9a9bdbdd?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">From idea to release, without the chaos</h3>
<p class="small mb-0 d-none d-sm-block">Automations take care of the repetitive steps, so people can focus on real work.</p>
</div>
</div>
</div>5Map placeholder
A 4:3 box reserved for a map, showing the address until the map loads.
Brio370 Maple Avenue, Singapore
<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>Brio</strong><span class="small text-body-secondary">370 Maple Avenue, Singapore</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-1702301266409-ed1bfe210971?auto=format&fit=crop&w=1200&h=800&q=70" alt="How remote teams keep projects on track" class="object-fit-cover">
</div>
<figcaption class="small text-body-secondary mt-1">3:2 · How to choose the right plan</figcaption>
</figure>7Portrait team cards
A 3:4 portrait ratio (133.33%) for team photos in cards.
Liam Harlow
Sales Executive
Nora Alvarez
Support Specialist
Ruby Ortega
Finance 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-1554902843-260acd0993f8?auto=format&fit=crop&w=1200&h=800&q=70" alt="Liam Harlow" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Liam Harlow</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-1690264351371-b75a9a9bdbdd?auto=format&fit=crop&w=1200&h=800&q=70" alt="Nora Alvarez" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Nora Alvarez</h3>
<p class="small text-body-secondary mb-0">Support Specialist</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-1690264421892-46e3af5c3455?auto=format&fit=crop&w=1200&h=800&q=70" alt="Ruby Ortega" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Ruby Ortega</h3>
<p class="small text-body-secondary mb-0">Finance 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.
EllaAria
MiaOwen<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-1742440710136-1976b1cad864?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Ella Lindqvist" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Ella</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-1690264351371-b75a9a9bdbdd?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Aria Mensah" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Aria</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-1531545514256-b1400bc00f31?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Mia Okafor" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Mia</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-1690264421892-46e3af5c3455?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Owen Tanaka" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Owen</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:58%">
</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:67%">
</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:35%">
</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:60%">
</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:88%">
</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:73%">
</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:78%">
</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.
insights
A practical guide to async work
Mar 24, 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-1690264351371-b75a9a9bdbdd?auto=format&fit=crop&w=1200&h=800&q=70" alt="How we cut our release cycle in half" class="object-fit-cover">
</div>
<div class="card-body">
<span class="badge text-bg-light border mb-2">insights</span>
<h3 class="h6">A practical guide to async work</h3>
<p class="small text-body-secondary mb-0">Mar 24, 2026</p>
</div>
</div>11Caption over a gradient
A 4:3 image with a gradient overlay so white caption text stays readable.
PortoSingle sign-on
<div class="ratio ratio-4x3 rounded-3 overflow-hidden" style="max-width:24rem">
<div>
<img src="https://images.unsplash.com/photo-1690264421892-46e3af5c3455?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">Porto</strong><span class="small">Single sign-on</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-1758691737124-05c5bffe46f0?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-1522202176988-66273c2fd55f?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-1690264459911-6d68c747d8a7?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-1690264421892-46e3af5c3455?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 |
|---|---|---|
| Starter plan | Free |
| Business plan | $47.00 |
 | API boost | $38.00 |
<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-1.svg" alt="Starter plan" class="object-fit-cover"></div></td>
<td class="align-middle">Starter plan</td>
<td class="align-middle text-end">Free</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-3.svg" alt="Business plan" class="object-fit-cover"></div></td>
<td class="align-middle">Business plan</td>
<td class="align-middle text-end">$47.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-11.svg" alt="API boost" class="object-fit-cover"></div></td>
<td class="align-middle">API boost</td>
<td class="align-middle text-end">$38.00</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" 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.
11:59NewThe small habits that make a big difference
13:05Five things we learned this year
13:49What our customers asked us most
<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-1554902843-260acd0993f8?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">11:59</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">The small habits that make a big difference</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1690264350953-79ef8acbd562?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">13:05</span>
</div>
</div>
<p class="small fw-semibold mt-1 mb-0">Five things we learned this year</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1742440710136-1976b1cad864?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">13:49</span>
</div>
</div>
<p class="small fw-semibold mt-1 mb-0">What our customers asked us most</p>
</div>
</div>17Media list
Fixed width 4:3 thumbnails beside article titles in a reading list.
Planning a product launch in six weeks
Sep 11, 2026 · 6 min read
Seven automations every team should set up
Apr 1, 2026 · 8 min read
Looking back at a busy season
Sep 17, 2026 · 11 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-1531545514256-b1400bc00f31?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">Planning a product launch in six weeks</h3><p class="small text-body-secondary mb-0">Sep 11, 2026 · 6 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-1690264421892-46e3af5c3455?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">Seven automations every team should set up</h3><p class="small text-body-secondary mb-0">Apr 1, 2026 · 8 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-1522202176988-66273c2fd55f?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">Looking back at a busy season</h3><p class="small text-body-secondary mb-0">Sep 17, 2026 · 11 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-1690264459911-6d68c747d8a7?auto=format&fit=crop&w=1600&h=700&q=70" alt="Turn scattered tasks into a clear plan" 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-7.svg" alt="Felix Delgado" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Felix</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-2.svg" alt="Theo Patel" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Theo</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-2.svg" alt="Isla Rossi" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Isla</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-5.svg" alt="Finn Okafor" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Finn</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>
</div>
<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>