About this site.

This is a set of free tools for working with slope — in a maths class, on a drawing, or on site. No accounts, no subscriptions, no advertising, and no step-by-step working hidden behind a paywall.

Why Build Another One

There is no shortage of slope calculators. Most of them share the same problems: they are slow, buried in advertising, they hand you a bare number with no indication of what it means, and several of them put the actual working — the part a student needs — behind a subscription.

There were also gaps that nothing seemed to fill. Every calculator treated slope as a dimensionless number, even though half the people looking for one are working in feet and inches. None of them let you share a calculation as a link. Almost all of them handled vertical lines badly, reporting infinity, an error, or nothing at all. And none of them answered the question people actually have, which is not “what is 20% as an angle” but “is 20% steep?”

The Principles

• Correct before anything else. Exact fractions rather than rounded decimals, every edge case handled on purpose, and an automated test suite behind it. The methodology page sets out the arithmetic in full, including what these tools deliberately do not do.
• Fast. Static pages, no framework, a few kilobytes of JavaScript, and self-hosted fonts. Nothing is fetched from a third party, so there is nothing to wait on and nothing tracking you across the web.
• Free, completely. Every result, the full working and the graph, with no account and no limit.
• Say what the number means. A grade of 8.33% is also 1:12, 4.76°, and the steepest ramp the ADA permits. That context is usually the reason someone opened a calculator at all.
• Usable by everyone. Full keyboard operation, labelled inputs, visible focus, a readable colour contrast, and a graph that describes itself to a screen reader instead of appearing as an unlabelled image.

Who It Is For

Three groups, with genuinely different needs, which is why the site is split the way it is. Students and teachers want exact fractions, every equation form and the working shown. Trades and site workers want feet and inches, percent grade, and a compliance answer. Everyone else has a specific question — how steep is that hill, will this ramp fit, how long is that rafter — and wants one number without reading an article first.

Using and Citing This Site

The calculators are free to use for any purpose, commercial work included. If you would like to put one on your own page, there is an embeddable version that needs a single line of HTML, loads nothing from anywhere else, and requires no attribution.

Sharing a result is just a matter of copying the address bar — the inputs are kept in the URL, so anyone who opens the link sees your calculation rather than an empty form.

On Accuracy

Considerable care has gone into getting the arithmetic and the cited standards right, and the reasoning is documented openly so it can be checked rather than taken on trust. Even so, these are tools to help you work, not a substitute for professional judgement. Anything that will be built should be confirmed against the code adopted in your jurisdiction and, where it matters, reviewed by a qualified professional.

If you find something wrong, please say so. A calculator that gives a wrong answer is worse than none.