HOLA-SERIES // ABOUT

A calculator that shows its working.

Most online calculators hand you a number and nothing else. You cannot see the formula, you cannot tell what was assumed, and you have no way to check whether the answer is right. We built the opposite: every tool here states its formula, explains what the result means, and shows a worked example you can reproduce.

The calculations run in your browser rather than on our servers. That is partly a speed decision and mostly a privacy one — a mortgage balance or a body weight is not something you should have to hand over to use a calculator.

Specifications

[PRV]Privacy

Client-side only

Every calculator runs inside your browser. The numbers you type are never transmitted to a server and never stored on one. There is no account to create, so there is nothing to leak.

[SPD]Response

Recalculates as you type

There is no Calculate button. Results update on every keystroke, which is what lets you change one input at a time and watch what it does to the answer.

[DOC]Documentation

Formula shown on every tool

Each calculator states the formula it applies, what the symbols mean, and a worked example computed from its own default values. You can check the result rather than trust it.

[CST]Cost

Free, no sign-up

No subscription, no paywall, no account. The site is funded by advertising, which is disclosed in full in the privacy policy.

[LNK]Sharing

State encoded in the URL

The Share button copies a link that reopens the calculator with your exact values filled in. Nothing is saved server-side to make that work.

[CNT]Library

166 calculators

Covering finance, mathematics and statistics, health and fitness, and everyday practical calculation. All of them work the same way.

What this is not

These are estimates, not advice. The financial tools apply standard formulas but cannot know your credit profile, your lender's fees, or the tax rules where you live. The health tools use population-level formulas that describe averages and will be wrong for individuals at the edges of a distribution.

Where a result would be expensive to get wrong — a loan you are about to sign, a material order, a clinical decision — treat the number here as the thing that tells you what question to ask a professional, not as the answer.

Suggest a calculator

The library grows based on what people ask for. If something you need is missing, or a formula here looks wrong to you, we want to know.