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="https://images.unsplash.com/photo-1762968274962-20c12e6e8ecd?auto=format&fit=crop&w=1600&h=700&q=70" 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.
Evening meetup
VIP pass
Student pass
Virtual pass
Full access pass
Recording 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-7.svg" alt="Evening meetup" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Evening meetup</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="VIP pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">VIP 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-8.svg" alt="Student pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Student 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="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-2.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-12.svg" alt="Recording pass" class="object-cover">
</div>
<p class="small truncate mt-1 mb-0">Recording pass</p>
</div>
</div>4Cinematic hero banner
ratio-21x9 for a wide banner with a headline overlay.
Where great ideas meet
<div class="ratio ratio-21x9 rounded-lg overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1560439514-0fc9d2cd5e1b?auto=format&fit=crop&w=1600&h=700&q=70" 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">Where great ideas meet</h3>
<p class="small mb-0 hidden sm:block">The venue is a short walk from the station and fully accessible.</p>
</div>
</div>
</div>5Map placeholder
A 4:3 box reserved for a map, showing the address until the map loads.
Bloomix Nest10 Lakeview Terrace, Singapore
<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-ink"><i class="bi bi-geo-alt-fill" aria-hidden="true"></i></span><strong>Bloomix Nest</strong><span class="small text-muted">10 Lakeview Terrace, 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-md overflow-hidden" style="--ui-aspect-ratio:66.67%">
<img src="https://images.unsplash.com/photo-1769755409781-9e8924c57362?auto=format&fit=crop&w=1200&h=800&q=70" alt="How to get the most out of a conference" class="object-cover">
</div>
<figcaption class="small text-muted mt-1">3:2 · A guide to the city for visiting attendees</figcaption>
</figure>7Portrait team cards
A 3:4 portrait ratio (133.33%) for team photos in cards.
Ivy Okafor
Content Writer
Ruby Ortega
Sales Executive
Mateo Haddad
Product Designer
<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="https://images.unsplash.com/photo-1773828755374-0ee802d9f44b?auto=format&fit=crop&w=1200&h=800&q=70" alt="Ivy Okafor" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Ivy Okafor</h3>
<p class="small text-muted mb-0">Content Writer</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="https://images.unsplash.com/photo-1769798643655-e0f10f62c3fd?auto=format&fit=crop&w=1200&h=800&q=70" alt="Ruby Ortega" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Ruby Ortega</h3>
<p class="small text-muted mb-0">Sales Executive</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="https://images.unsplash.com/photo-1769798643655-e0f10f62c3fd?auto=format&fit=crop&w=1200&h=800&q=70" alt="Mateo Haddad" class="object-cover">
</div>
<div class="card-body py-2">
<h3 class="h6 mb-0">Mateo Haddad</h3>
<p class="small text-muted mb-0">Product Designer</p>
</div>
</div>
</div>
</div>8Vertical stories
A 9:16 ratio (177.78%) for phone sized stories or short clips in a scrolling row.
Liam
Kai
Mason
Ella<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="https://images.unsplash.com/photo-1560523159-94c9d18bcf27?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Liam Harlow" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Liam</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="https://images.unsplash.com/photo-1560439514-0fc9d2cd5e1b?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Kai Ibrahim" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Kai</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="https://images.unsplash.com/photo-1560523159-fbe43c0b465f?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Mason Moreau" 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="https://images.unsplash.com/photo-1780413462971-e245268a13d2?auto=format&fit=crop&w=1200&h=800&q=70" alt="Story by Ella Tanaka" class="w-full h-full object-cover"><span class="absolute bottom-0 start-0 m-1 badge text-bg-dark">Ella</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:65%">
</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:39%">
</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:41%">
</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:27%">
</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:69%">
</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:69%">
</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:87%">
</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:52%">
</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
What we learned from last year's feedback
Jan 16, 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-1560439514-0fc9d2cd5e1b?auto=format&fit=crop&w=1200&h=800&q=70" alt="The small habits that make a big difference" class="object-cover">
</div>
<div class="card-body">
<span class="badge text-bg-light border mb-2">tutorial</span>
<h3 class="h6">What we learned from last year's feedback</h3>
<p class="small text-muted mb-0">Jan 16, 2026</p>
</div>
</div>11Caption over a gradient
A 4:3 image with a gradient overlay so white caption text stays readable.
DenverVenue booking
<div class="ratio ratio-4x3 rounded-lg overflow-hidden" style="max-width:24rem">
<div>
<img src="https://images.unsplash.com/photo-1780413462971-e245268a13d2?auto=format&fit=crop&w=1200&h=800&q=70" 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">Denver</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="https://images.unsplash.com/photo-1773829020694-413e879d2957?auto=format&fit=crop&w=1200&h=800&q=70" 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="https://images.unsplash.com/photo-1762968269894-1d7e1ce8894e?auto=format&fit=crop&w=800&h=800&q=70" alt="Gallery photo 2" class="object-cover">
</div>
</div>
<div class="col-6">
<div class="ratio ratio-1x1 rounded-md overflow-hidden">
<img src="https://images.unsplash.com/photo-1770097286213-6d6fc60f4cdf?auto=format&fit=crop&w=800&h=800&q=70" alt="Gallery photo 3" class="object-cover">
</div>
</div>
<div class="col-12">
<div class="ratio ratio-21x9 rounded-md overflow-hidden">
<img src="https://images.unsplash.com/photo-1780413462971-e245268a13d2?auto=format&fit=crop&w=1600&h=700&q=70" 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 |
|---|---|---|
| Recording pass | $58.00 |
 | Group bundle | $2,050 |
 | Masterclass | $254.00 |
<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-12.svg" alt="Recording pass" class="object-cover"></div></td>
<td class="align-middle">Recording pass</td>
<td class="align-middle text-end">$58.00</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded-md overflow-hidden"><img src="../assets/img/product-6.svg" alt="Group bundle" class="object-cover"></div></td>
<td class="align-middle">Group bundle</td>
<td class="align-middle text-end">$2,050</td>
</tr>
<tr>
<td style="width:4rem"><div class="ratio ratio-1x1 rounded-md overflow-hidden"><img src="../assets/img/product-9.svg" alt="Masterclass" class="object-cover"></div></td>
<td class="align-middle">Masterclass</td>
<td class="align-middle text-end">$254.00</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 wt-border-dashed">
<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.
7:25NewFive things we learned this year
4:06What makes a panel worth watching
9:58How to choose the right ticket
<div class="row g-3">
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded-md overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1769798643655-e0f10f62c3fd?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-full h-full object-cover"><span class="absolute bottom-0 end-0 m-2 badge text-bg-dark">7:25</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">Five things we learned this year</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded-md overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1762968274962-20c12e6e8ecd?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-full h-full object-cover"><span class="absolute bottom-0 end-0 m-2 badge text-bg-dark">4:06</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">What makes a panel worth watching</p>
</div>
<div class="col-md-4">
<div class="ratio ratio-16x9 rounded-md overflow-hidden">
<div>
<img src="https://images.unsplash.com/photo-1560523159-94c9d18bcf27?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="w-full h-full object-cover"><span class="absolute bottom-0 end-0 m-2 badge text-bg-dark">9:58</span>
</div>
</div>
<p class="small font-semibold mt-1 mb-0">How to choose the right ticket</p>
</div>
</div>17Media list
Fixed width 4:3 thumbnails beside article titles in a reading list.
Looking back at a busy season
Jul 19, 2026 · 11 min read
Highlights from last year's workshops
Sep 23, 2025 · 6 min read
What our attendees asked us most
Jan 16, 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="https://images.unsplash.com/photo-1560523159-fbe43c0b465f?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-cover"></div></div><div><h3 class="h6 mb-1">Looking back at a busy season</h3><p class="small text-muted mb-0">Jul 19, 2026 · 11 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="https://images.unsplash.com/photo-1780413462971-e245268a13d2?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-cover"></div></div><div><h3 class="h6 mb-1">Highlights from last year's workshops</h3><p class="small text-muted mb-0">Sep 23, 2025 · 6 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="https://images.unsplash.com/photo-1762968269894-1d7e1ce8894e?auto=format&fit=crop&w=1200&h=800&q=70" alt="" class="object-cover"></div></div><div><h3 class="h6 mb-1">What our attendees asked us most</h3><p class="small text-muted mb-0">Jan 16, 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="https://images.unsplash.com/photo-1770097286213-6d6fc60f4cdf?auto=format&fit=crop&w=1600&h=700&q=70" alt="Learn from the best, meet the rest" 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-12.svg" alt="Samir Kowalski" class="object-cover">
</div>
<span class="small block truncate mt-1">Samir</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="Freya Patel" class="object-cover">
</div>
<span class="small block truncate mt-1">Freya</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-10.svg" alt="Diego Kim" class="object-cover">
</div>
<span class="small block truncate mt-1">Diego</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-9.svg" alt="Aria Ortega" class="object-cover">
</div>
<span class="small block truncate mt-1">Aria</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>