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.
Vaccination
Video consult
Dental cleaning
Blood test
Physio session
Annual check-up
<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="Vaccination" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Vaccination</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="Video consult" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Video consult</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="Dental cleaning" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Dental cleaning</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="Blood test" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Blood test</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="Physio session" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Physio session</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="Annual check-up" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Annual check-up</p>
</div>
</div>4Cinematic hero banner
ratio-21x9 for a wide banner with a headline overlay.
Care that puts you first
<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">Care that puts you first</h3>
<p class="small mb-0 hidden sm:block">This focused team makes the whole team on the same page on any device.</p>
</div>
</div>
</div>5Map placeholder
A 4:3 box reserved for a map, showing the address until the map loads.
Brand name 15181 Station Street, Prague
<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 15</strong><span class="small text-muted">181 Station Street, Prague</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 dental care" class="object-cover">
</div>
<figcaption class="small text-muted mt-1">3:2 · What's new in orthopedics</figcaption>
</figure>7Portrait team cards
A 3:4 portrait ratio (133.33%) for team photos in cards.
Nadia Brennan
HR Partner
Ruby Larsen
Backend Engineer
Freya Whitaker
Frontend Engineer
<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-12.svg" alt="Nadia Brennan" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Nadia Brennan</h3>
<p class="small text-muted mb-0">HR Partner</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-6.svg" alt="Ruby Larsen" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Ruby Larsen</h3>
<p class="small text-muted mb-0">Backend Engineer</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-1.svg" alt="Freya Whitaker" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Freya Whitaker</h3>
<p class="small text-muted mb-0">Frontend Engineer</p>
</div>
</div>
</div>
</div>8Vertical stories
A 9:16 ratio (177.78%) for phone sized stories or short clips in a scrolling row.
Mason
Nadia
Chloe
Lea<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 Mason Ashford" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Mason</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 Nadia Harlow" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Nadia</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 Chloe Fischer" 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 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 Lea Patel" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Lea</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:45%">
</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:77%">
</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:90%">
</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:82%">
</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:23%">
</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:65%">
</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:42%">
</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:64%">
</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.
tutorial
The focused dashboard checklist
Jun 10, 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="9 lessons from our launch" class="object-cover">
</div>
<div class="card-body">
<span class="badge text-bg-light border mb-2">tutorial</span>
<h3 class="h6">The focused dashboard checklist</h3>
<p class="small text-muted mb-0">Jun 10, 2026</p>
</div>
</div>11Caption over a gradient
A 4:3 image with a gradient overlay so white caption text stays readable.
DublinLab tests
<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">Dublin</strong><span class="small">Lab tests</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 |
|---|---|---|
| Video consult | $461.00 |
| Vaccination | $94.50 |
| Physio session | $440.00 |
<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="Video consult" class="object-cover"></div></td>
<td class="align-middle">Video consult</td>
<td class="align-middle text-end">$461.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded-md overflow-hidden"><img src="../assets/img/product-2.svg" alt="Vaccination" class="object-cover"></div></td>
<td class="align-middle">Vaccination</td>
<td class="align-middle text-end">$94.50</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded-md overflow-hidden"><img src="../assets/img/product-3.svg" alt="Physio session" class="object-cover"></div></td>
<td class="align-middle">Physio session</td>
<td class="align-middle text-end">$440.00</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" 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.
6:44New5 lessons from our idea
12:30How we rebuilt our routine
12:16The reliable routine checklist
<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">6:44</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">5 lessons from our idea</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">12:30</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">How we rebuilt our routine</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">12:16</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">The reliable routine checklist</p>
</div>
</div>17Media list
Fixed width 4:3 thumbnails beside article titles in a reading list.
What's new in dental
Oct 21, 2025 · 8 min read
Idea notes for patients
Dec 4, 2025 · 10 min read
3 lessons from our journey
Feb 5, 2026 · 12 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">What's new in dental</h3><p class="small text-muted mb-0">Oct 21, 2025 · 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">Idea notes for patients</h3><p class="small text-muted mb-0">Dec 4, 2025 · 10 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">3 lessons from our journey</h3><p class="small text-muted mb-0">Feb 5, 2026 · 12 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="Feel better with expert care" 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-9.svg" alt="Priya Duarte" class="object-cover">
</div>
<span class="small block truncate mt-1">Priya</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-11.svg" alt="Ruby Delgado" 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-8.svg" alt="Ella Okafor" class="object-cover">
</div>
<span class="small block truncate mt-1">Ella</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-3.svg" alt="Zoe Silva" class="object-cover">
</div>
<span class="small block truncate mt-1">Zoe</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>