Web & design calculators
6 free tools
Small, practical tools for the numbers that come up when you build or design for the web. Estimate how long a download will take, check a screen's pixel density, size up an image before you ship it, plan for a month of traffic, resize while keeping the aspect ratio, and set a comfortable line length for reading.
Scale an image or video to a new width or height while keeping its original proportions.
Estimate your website's monthly bandwidth from page size, visitor count, and pages per visit.
Estimate how long a file takes to download from its size and your connection speed, with bits and bytes sorted out.
Estimate the uncompressed size of an image from its dimensions and bit depth, with a rough JPEG figure too.
Work out a display's pixels per inch and dot pitch from its resolution and diagonal size.
Turn your font size and a target line length into the ideal content column width in pixels.
Frequently asked questions
Do I need to sign up to use these?
No. Every tool runs entirely in your browser, so there's nothing to install and no account to create. Type your numbers in and read the result.
Why do the estimates differ from what I see in real life?
These are honest back-of-the-envelope figures. Download speeds drop below the advertised rate, JPEG compression depends on the image, and real page sizes vary — treat the results as planning numbers, not guarantees.
Which units should I use?
Each tool spells out its units next to the field, like MB, Mbps, pixels, or inches. Watch the bits-versus-bytes distinction on the download tool especially — that's the one people trip over most.