About RatioForge
RatioForge is a free aspect ratio calculator built around one idea: the simplest jobs should not need an account, an upload, or a wait.
What it does
RatioForge turns an aspect ratio and a single dimension into the matching dimension. Pick a ratio such as 16:9, type a width or a height, and the other side appears instantly. You can switch units between pixels, centimetres, inches and millimetres, lock a ratio while you resize, drop an image to read its ratio automatically, and copy or share the result with a single click.
Why we built it
Most aspect ratio tools are heavier than the task deserves — pop-ups, sign-ups, sluggish pages. We wanted the opposite: open the page, get your number, move on. The whole calculator is a single, lightweight page that loads fast and works the same on a phone, tablet or desktop.
How it works
Everything runs in your browser. When you drop an image to detect its ratio, the file is read locally to measure its pixel dimensions and is never uploaded to a server. There is no backend processing your data, because there is no need for one — the maths is simple enough to do instantly on your device.
How we calculate ratios
The maths is deliberately simple and transparent. To simplify a ratio, RatioForge divides the width and height by their greatest common divisor (GCD): 1920 and 1080 share a GCD of 120, so 1920:1080 reduces to 16:9. To find a missing side it multiplies by the ratio — height = width × ratioHeight ÷ ratioWidth — and rounds to a whole pixel (or two decimals for centimetres and inches). The calculation runs live in your browser, so the same input always produces the same result, with nothing sent to a server.
Who it's for
- Video creators sizing thumbnails, exports and vertical clips.
- Social media managers matching each platform's preferred dimensions.
- Designers and developers keeping images and layouts proportional.
- Photographers cropping to print sizes without distortion.
- Anyone who just needs "if the width is X, what is the height?"
Who runs RatioForge
RatioForge is built and maintained by the RatioForge team, an independent project operated by bsgoods, based in the Netherlands. RatioForge has a sister site, TokenForge — a free LLM token cost calculator built on the same principles: fast, free, in-browser, no accounts. It is not affiliated with the platforms it references — YouTube, Instagram, TikTok and others; those names and specifications belong to their respective owners and are provided for guidance only. Spotted a mistake or have a request? Get in touch — the same people who build the tool read the messages.
Privacy and ads
RatioForge has no accounts and collects no personal data. It is free to use, and the running costs are covered by advertising through Google AdSense. We use Google Consent Mode, so advertising cookies stay disabled until you choose to accept them. The full details are in our privacy policy.
Learn more
New to aspect ratios? Start with our guides — including aspect ratios explained and the social media image size reference. Got feedback or a request? Get in touch.