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-1689877020200-403d8542d95d?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.
Spin class pack
Yoga retreat
Sauna session
Massage
Mobility workshop
Day pass
<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-7.svg" alt="Spin class pack" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Spin class 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="Yoga retreat" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Yoga retreat</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="Sauna session" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Sauna session</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="Massage" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Massage</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded overflow-hidden border">
<img src="../assets/img/product-10.svg" alt="Mobility workshop" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Mobility workshop</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="Day pass" class="object-fit-cover">
</div>
<p class="small text-truncate mt-1 mb-0">Day pass</p>
</div>
</div>4Cinematic hero banner
ratio-21x9 for a wide banner with a headline overlay.
Find the workout you will love
We keep things simple, so you can focus on what matters to you.
<div class="ratio ratio-21x9 rounded-3 overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1778828494354-9b717d36dc99?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">Find the workout you will love</h3>
<p class="small mb-0 d-none d-sm-block">We keep things simple, so you can focus on what matters to you.</p>
</div>
</div>
</div>5Map placeholder
A 4:3 box reserved for a map, showing the address until the map loads.
Sageo Studio445 Maple Avenue, Valencia
<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>Sageo Studio</strong><span class="small text-body-secondary">445 Maple Avenue, Valencia</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-1599058917212-d750089bc07e?auto=format&fit=crop&w=1200&h=800&q=70" alt="Our most popular classes this month" class="object-fit-cover">
</div>
<figcaption class="small text-body-secondary mt-1">3:2 · How our coaches plan a new class</figcaption>
</figure>7Portrait team cards
A 3:4 portrait ratio (133.33%) for team photos in cards.
Ava Rossi
QA Engineer
Ravi Moreau
Marketing Lead
Aria Delgado
Data Analyst
<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-1583454110551-21f2fa2afe61?auto=format&fit=crop&w=1200&h=800&q=70" alt="Ava Rossi" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Ava Rossi</h3>
<p class="small text-body-secondary mb-0">QA Engineer</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-1583454110551-21f2fa2afe61?auto=format&fit=crop&w=1200&h=800&q=70" alt="Ravi Moreau" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Ravi Moreau</h3>
<p class="small text-body-secondary mb-0">Marketing Lead</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-1583454110551-21f2fa2afe61?auto=format&fit=crop&w=1200&h=800&q=70" alt="Aria Delgado" class="object-fit-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Aria Delgado</h3>
<p class="small text-body-secondary mb-0">Data Analyst</p>
</div>
</div>
</div>
</div>8Vertical stories
A 9:16 ratio (177.78%) for phone sized stories or short clips in a scrolling row.
Mateo
Jonah
Liam
Zoe<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-1541534741688-6078c6bfb5c5?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Mateo Morgan" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Mateo</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-1778828494354-9b717d36dc99?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Jonah Novak" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Jonah</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-1574680096145-d05b474e2155?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Liam Sato" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Liam</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-1641337221253-fdc7237f6b61?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Zoe Tanaka" class="w-100 h-100 object-fit-cover"><span class="position-absolute bottom-0 start-0 m-1 badge text-bg-dark">Zoe</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:35%">
</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:41%">
</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:79%">
</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:20%">
</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:70%">
</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:36%">
</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:53%">
</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:20%">
</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 beginner's guide to strength training
Sep 18, 2025
<div class="card" style="max-width:22rem">
<div class="ratio ratio-16x9 card-img-top overflow-hidden">
<img src="https://images.unsplash.com/photo-1778828494354-9b717d36dc99?auto=format&fit=crop&w=1200&h=800&q=70" alt="How to stay motivated through winter" class="object-fit-cover">
</div>
<div class="card-body">
<span class="badge text-bg-light border mb-2">insights</span>
<h3 class="h6">A beginner's guide to strength training</h3>
<p class="small text-body-secondary mb-0">Sep 18, 2025</p>
</div>
</div>11Caption over a gradient
A 4:3 image with a gradient overlay so white caption text stays readable.
MontrealOnline coaching
<div class="ratio ratio-4x3 rounded-3 overflow-hidden" style="max-width:24rem">
<div>
<img src="https://images.unsplash.com/photo-1641337221253-fdc7237f6b61?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">Montreal</strong><span class="small">Online coaching</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-1761839258420-5c3e2f2e2a74?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-1583454110551-21f2fa2afe61?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-1554284126-aa88f22d8b74?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-1641337221253-fdc7237f6b61?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 |
|---|---|---|
| Yoga retreat | $390.00 |
 | 10-class pack | $122.00 |
 | Monthly pass | $49.00 |
<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="Yoga retreat" class="object-fit-cover"></div></td>
<td class="align-middle">Yoga retreat</td>
<td class="align-middle text-end">$390.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-2.svg" alt="10-class pack" class="object-fit-cover"></div></td>
<td class="align-middle">10-class pack</td>
<td class="align-middle text-end">$122.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded overflow-hidden"><img src="../assets/img/product-1.svg" alt="Monthly pass" class="object-fit-cover"></div></td>
<td class="align-middle">Monthly pass</td>
<td class="align-middle text-end">$49.00</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.
9:26NewFive stretches for desk workers
14:02Five things we learned this year
7:04Why recovery matters as much as training
<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-1758875569612-94d5e0f1a35f?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">9:26</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">Five stretches for desk workers</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1689877020200-403d8542d95d?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">14:02</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-1541534741688-6078c6bfb5c5?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">7:04</span>
</div>
</div>
<p class="small fw-semibold mt-1 mb-0">Why recovery matters as much as training</p>
</div>
</div>17Media list
Fixed width 4:3 thumbnails beside article titles in a reading list.
Our favourite tips for busy weeks
Nov 5, 2025 · 9 min read
The small habits that make a big difference
Oct 4, 2025 · 8 min read
HIIT twice a week: how hard is hard enough?
Mar 18, 2026 · 8 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-1574680096145-d05b474e2155?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">Our favourite tips for busy weeks</h3><p class="small text-body-secondary mb-0">Nov 5, 2025 · 9 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-1641337221253-fdc7237f6b61?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">The small habits that make a big difference</h3><p class="small text-body-secondary mb-0">Oct 4, 2025 · 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-1583454110551-21f2fa2afe61?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-fit-cover"></div></div><div><h3 class="h6 mb-1">HIIT twice a week: how hard is hard enough?</h3><p class="small text-body-secondary mb-0">Mar 18, 2026 · 8 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-1554284126-aa88f22d8b74?auto=format&fit=crop&w=1600&h=700&q=70" alt="Move more, stress less" 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-3.svg" alt="Tariq Quinn" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Tariq</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-12.svg" alt="Chloe Nguyen" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Chloe</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-8.svg" alt="Ella Haddad" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Ella</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="Noah Fischer" class="object-fit-cover">
</div>
<span class="small d-block text-truncate mt-1">Noah</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>