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="flex items-center justify-center bg-primary-subtle text-primary-emphasis border border-primary/30 rounded-md font-semibold">
1:1
</div>
</div>
</div>
<div class="col-6 col-md-3">
<div class="ratio ratio-4x3">
<div class="flex items-center justify-center bg-primary-subtle text-primary-emphasis border border-primary/30 rounded-md font-semibold">
4:3
</div>
</div>
</div>
<div class="col-6 col-md-3">
<div class="ratio ratio-16x9">
<div class="flex items-center justify-center bg-primary-subtle text-primary-emphasis border border-primary/30 rounded-md font-semibold">
16:9
</div>
</div>
</div>
<div class="col-6 col-md-3">
<div class="ratio ratio-21x9">
<div class="flex items-center justify-center bg-primary-subtle text-primary-emphasis border border-primary/30 rounded-md font-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-md overflow-hidden" style="max-width:36rem">
<div>
<img src="../assets/img/wide-2.svg" alt="Video poster" class="w-full h-full object-cover">
<button type="button" class="btn btn-light rounded-full absolute top-1/2 start-1/2 -translate-x-1/2 -translate-y-1/2 shadow-md" 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.
Early bird pass
Virtual pass
Group bundle
Full access pass
Workshop ticket
VIP pass
<div class="row g-2">
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-md overflow-hidden border">
<img src="../assets/img/product-1.svg" alt="Early bird pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Early bird pass</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-md overflow-hidden border">
<img src="../assets/img/product-2.svg" alt="Virtual pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Virtual pass</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-md overflow-hidden border">
<img src="../assets/img/product-3.svg" alt="Group bundle" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Group bundle</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-md overflow-hidden border">
<img src="../assets/img/product-4.svg" alt="Full access pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Full access pass</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-md overflow-hidden border">
<img src="../assets/img/product-5.svg" alt="Workshop ticket" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Workshop ticket</p>
</div>
<div class="col-4 col-md-2">
<div class="ratio ratio-1x1 rounded-md overflow-hidden border">
<img src="../assets/img/product-6.svg" alt="VIP pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">VIP pass</p>
</div>
</div>4Cinematic hero banner
ratio-21x9 for a wide banner with a headline overlay.
Learn, connect and get inspired
<div class="ratio ratio-21x9 rounded-lg overflow-hidden">
<div>
<img src="../assets/img/wide-4.svg" alt="" class="w-full h-full object-cover">
<div class="absolute bottom-0 start-0 p-4 md:p-6 text-white" style="background:rgba(0,0,0,.45)">
<h3 class="h4 mb-1">Learn, connect and get inspired</h3>
<p class="small mb-0 hidden sm:block">Our sponsorship guides you focused on what matters all year round.</p>
</div>
</div>
</div>5Map placeholder
A 4:3 box reserved for a map, showing the address until the map loads.
Brand name 20202 Station Street, Copenhagen
<div class="ratio ratio-4x3" style="max-width:24rem">
<div class="flex flex-col items-center justify-center bg-surface-3 border rounded-md text-center p-4">
<span class="text-4xl text-primary"><i class="bi bi-geo-alt-fill" aria-hidden="true"></i></span><strong>Brand name 20</strong><span class="small text-muted">202 Station Street, Copenhagen</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-md overflow-hidden" style="--ui-aspect-ratio:66.67%">
<img src="../assets/img/photo-3.svg" alt="A guide to speaker management" class="object-cover">
</div>
<figcaption class="small text-muted mt-1">3:2 · A guide to venue booking</figcaption>
</figure>7Portrait team cards
A 3:4 portrait ratio (133.33%) for team photos in cards.
Nora Haddad
Data Analyst
Isla Mensah
Operations Manager
Priya Whitaker
Marketing Lead
<div class="row g-3">
<div class="col-6 col-md-4">
<div class="card h-full">
<div class="ratio card-img-top overflow-hidden" style="--ui-aspect-ratio:133.33%">
<img src="../assets/img/photo-2.svg" alt="Nora Haddad" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Nora Haddad</h3>
<p class="small text-muted mb-0">Data Analyst</p>
</div>
</div>
</div>
<div class="col-6 col-md-4">
<div class="card h-full">
<div class="ratio card-img-top overflow-hidden" style="--ui-aspect-ratio:133.33%">
<img src="../assets/img/photo-5.svg" alt="Isla Mensah" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Isla Mensah</h3>
<p class="small text-muted mb-0">Operations Manager</p>
</div>
</div>
</div>
<div class="col-6 col-md-4">
<div class="card h-full">
<div class="ratio card-img-top overflow-hidden" style="--ui-aspect-ratio:133.33%">
<img src="../assets/img/photo-5.svg" alt="Priya Whitaker" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Priya Whitaker</h3>
<p class="small text-muted 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.
Diego
Mateo
Zoe
Chloe<div class="flex gap-2 overflow-auto pb-1">
<div class="shrink-0" style="width:7rem">
<div class="ratio rounded-lg overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="../assets/img/photo-6.svg" alt="Story by Diego Brennan" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Diego</span>
</div>
</div>
</div>
<div class="shrink-0" style="width:7rem">
<div class="ratio rounded-lg overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="../assets/img/photo-7.svg" alt="Story by Mateo Haddad" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Mateo</span>
</div>
</div>
</div>
<div class="shrink-0" style="width:7rem">
<div class="ratio rounded-lg overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="../assets/img/photo-8.svg" alt="Story by Zoe Hughes" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Zoe</span>
</div>
</div>
</div>
<div class="shrink-0" style="width:7rem">
<div class="ratio rounded-lg overflow-hidden" style="--ui-aspect-ratio:177.78%">
<div>
<img src="../assets/img/photo-9.svg" alt="Story by Chloe Varga" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Chloe</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 font-semibold">
Monthly bookings
</div>
<div class="card-body">
<div class="ratio ratio-16x9">
<div class="flex items-end gap-2" role="img" aria-label="Bar chart of monthly bookings">
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:41%">
</div>
<span class="small text-muted">Jan</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:21%">
</div>
<span class="small text-muted">Feb</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:45%">
</div>
<span class="small text-muted">Mar</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:56%">
</div>
<span class="small text-muted">Apr</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:46%">
</div>
<span class="small text-muted">May</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:32%">
</div>
<span class="small text-muted">Jun</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:64%">
</div>
<span class="small text-muted">Jul</span>
</div>
<div class="flex-auto flex flex-col justify-end items-center h-full">
<div class="w-full bg-primary rounded-t-md" style="height:37%">
</div>
<span class="small text-muted">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.
update
Inside the secure workflow
Mar 9, 2026
<div class="card" style="max-width:22rem">
<div class="ratio ratio-16x9 card-img-top overflow-hidden">
<img src="../assets/img/photo-7.svg" alt="How we rebuilt our idea" class="object-cover">
</div>
<div class="card-body">
<span class="badge text-bg-light border mb-2">update</span>
<h3 class="h6">Inside the secure workflow</h3>
<p class="small text-muted mb-0">Mar 9, 2026</p>
</div>
</div>11Caption over a gradient
A 4:3 image with a gradient overlay so white caption text stays readable.
KyotoVenue booking
<div class="ratio ratio-4x3 rounded-lg overflow-hidden" style="max-width:24rem">
<div>
<img src="../assets/img/photo-9.svg" alt="" class="w-full h-full object-cover">
<div class="absolute bottom-0 w-full p-4 text-white" style="background:linear-gradient(transparent,rgba(0,0,0,.7))">
<strong class="block">Kyoto</strong><span class="small">Venue booking</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-md overflow-hidden">
<img src="../assets/img/photo-2.svg" alt="Gallery photo 1" class="object-cover">
</div>
</div>
<div class="col-md-6">
<div class="row g-2">
<div class="col-6">
<div class="ratio ratio-1x1 rounded-md overflow-hidden">
<img src="../assets/img/square-4.svg" alt="Gallery photo 2" class="object-cover">
</div>
</div>
<div class="col-6">
<div class="ratio ratio-1x1 rounded-md overflow-hidden">
<img src="../assets/img/square-5.svg" alt="Gallery photo 3" class="object-cover">
</div>
</div>
<div class="col-12">
<div class="ratio ratio-21x9 rounded-md overflow-hidden">
<img src="../assets/img/wide-6.svg" alt="Gallery photo 4" class="object-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 |
|---|---|---|
| Virtual pass | $160.00 |
| Early bird pass | $360.50 |
| VIP pass | $100.00 |
<table class="table align-middle mb-0">
<thead>
<tr>
<th scope="col"><span class="sr-only">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-md overflow-hidden"><img src="../assets/img/product-1.svg" alt="Virtual pass" class="object-cover"></div></td>
<td class="align-middle">Virtual pass</td>
<td class="align-middle text-end">$160.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded-md overflow-hidden"><img src="../assets/img/product-2.svg" alt="Early bird pass" class="object-cover"></div></td>
<td class="align-middle">Early bird pass</td>
<td class="align-middle text-end">$360.50</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded-md overflow-hidden"><img src="../assets/img/product-3.svg" alt="VIP pass" class="object-cover"></div></td>
<td class="align-middle">VIP pass</td>
<td class="align-middle text-end">$100.00</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="flex flex-col items-center justify-center border border-2 border-secondary/30 rounded-lg text-muted" style="border-style:dashed!important">
<span class="text-3xl"><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-lg bg-primary">
<span class="sr-only">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-lg bg-secondary">
<span class="sr-only">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-lg bg-success">
<span class="sr-only">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-lg bg-info">
<span class="sr-only">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-lg bg-warning">
<span class="sr-only">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-lg bg-danger">
<span class="sr-only">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.
3:01NewThe practical team checklist
10:13How we rebuilt our update
10:52Friendly ways to improve your idea
<div class="row g-3">
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded-md overflow-hidden">
<div>
<img src="../assets/img/photo-4.svg" alt="" class="w-full h-full object-cover"><span class="absolute bottom-0 end-0 m-2 badge text-bg-dark">3:01</span><span class="absolute top-0 start-0 m-2 badge text-bg-danger">New</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">The practical team checklist</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded-md overflow-hidden">
<div>
<img src="../assets/img/photo-5.svg" alt="" class="w-full h-full object-cover"><span class="absolute bottom-0 end-0 m-2 badge text-bg-dark">10:13</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">How we rebuilt our update</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded-md overflow-hidden">
<div>
<img src="../assets/img/photo-6.svg" alt="" class="w-full h-full object-cover"><span class="absolute bottom-0 end-0 m-2 badge text-bg-dark">10:52</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">Friendly ways to improve your idea</p>
</div>
</div>17Media list
Fixed width 4:3 thumbnails beside article titles in a reading list.
Inside the fast plan
May 3, 2026 · 8 min read
Secure ways to improve your experience
Jan 3, 2026 · 7 min read
Elegant ways to improve your launch
Feb 5, 2026 · 4 min read
<ul class="list-unstyled mb-0 vstack gap-4">
<li class="flex gap-4"><div class="shrink-0" style="width:6rem"><div class="ratio ratio-4x3 rounded-md overflow-hidden"><img src="../assets/img/photo-8.svg" alt="" class="object-cover"></div></div><div><h3 class="h6 mb-1">Inside the fast plan</h3><p class="small text-muted mb-0">May 3, 2026 · 8 min read</p></div></li>
<li class="flex gap-4"><div class="shrink-0" style="width:6rem"><div class="ratio ratio-4x3 rounded-md overflow-hidden"><img src="../assets/img/photo-9.svg" alt="" class="object-cover"></div></div><div><h3 class="h6 mb-1">Secure ways to improve your experience</h3><p class="small text-muted mb-0">Jan 3, 2026 · 7 min read</p></div></li>
<li class="flex gap-4"><div class="shrink-0" style="width:6rem"><div class="ratio ratio-4x3 rounded-md overflow-hidden"><img src="../assets/img/photo-10.svg" alt="" class="object-cover"></div></div><div><h3 class="h6 mb-1">Elegant ways to improve your launch</h3><p class="small text-muted mb-0">Feb 5, 2026 · 4 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-lg overflow-hidden">
<img src="../assets/img/wide-8.svg" alt="Three days that change how you work" class="object-cover">
</div>19Round avatars
ratio-1x1 with rounded-circle keeps profile pictures perfectly round even when the source is not square.
<div class="flex flex-wrap gap-4">
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-full overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-5.svg" alt="Sofia Duarte" class="object-cover">
</div>
<span class="small block truncate mt-1">Sofia</span>
</div>
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-full overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-4.svg" alt="Ruby Nguyen" class="object-cover">
</div>
<span class="small block truncate mt-1">Ruby</span>
</div>
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-full overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-7.svg" alt="Tariq Hughes" class="object-cover">
</div>
<span class="small block truncate mt-1">Tariq</span>
</div>
<div class="text-center" style="width:5rem">
<div class="ratio ratio-1x1 rounded-full overflow-hidden border border-2 border-primary">
<img src="../assets/img/avatar-7.svg" alt="Tariq Larsen" class="object-cover">
</div>
<span class="small block truncate mt-1">Tariq</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-muted mt-2 mb-0">The skeleton reserves the exact space, so the page does not jump when content arrives.</p>