About RatioCalc
RatioCalc started with a small, recurring annoyance. Every time we needed to resize a thumbnail, check whether a client's video matched a 16:9 timeline, or figure out how tall a 1200-pixel-wide banner should be, we ended up either doing the arithmetic by hand or wading through calculator sites buried under pop-ups and cluttered layouts.
So we built the tool we wanted to use: one clean page that answers both of the questions people actually ask about aspect ratios —
- "What ratio is this?" — enter any width and height, get the simplified ratio instantly.
- "How big should the other side be?" — lock a ratio, enter one dimension, get the other.
Who this is for
Mostly people who work with images and video every day: YouTubers sizing thumbnails, social media managers preparing assets for five platforms at once, designers matching canvases to device specs, photographers cropping for print, and developers who just need the math done without opening a spreadsheet.
How the site is funded
RatioCalc is free and will stay free. The site is supported by a small number of display advertisements. We deliberately keep ad placements away from the calculator itself so they never interfere with the tool. If you'd like to know how advertising affects your privacy, our privacy policy explains it in plain language.
Accuracy
Ratio simplification uses the greatest-common-divisor method, with decimal ratios (like cinema's 2.39:1) handled by fixed-precision scaling. Calculated dimensions are rounded to the nearest whole pixel, since displays can't render fractional pixels — the rounding error is always under one pixel. If you ever spot a result that looks wrong, please tell us and we'll investigate.
What's next
We maintain a growing set of plain-English guides covering platform-specific dimensions — YouTube, Instagram, TikTok, and more — that we update whenever platforms change their specs. If there's a ratio, platform, or feature you'd like covered, we're listening.