Calculators
Calculators for health and math. Each one shows the formula it uses, where the formula comes from, and how to read the result.
10 Calculators
2 Categories
Sourced & Verified
Math
6Featured Calculators
Frequently Asked Questions
Are these calculators accurate?
Formulas come from authoritative references: WHO guidance for health calculations, standard mathematical definitions for math tools, and financial industry conventions for finance calculators. Every calculation is checked against known test cases, and each page states the assumptions its formula makes.What formulas do you use?
Each calculator page displays the exact formula used. For example, BMI uses weight (kg) / height² (m²). All formulas are documented with variable definitions and unit requirements.How is this different from a regular calculator?
Each page is built around one formula. It labels the inputs, handles unit conversion, shows the equation, and explains what the result means — so you do not need to remember the formula or convert units yourself.
How these calculators work
Every calculator here is generated from a formula registry: the expression, its variables, their units, and the reference it comes from. The worked example runs the same maths as the input panel.
Results recompute in the browser as you type — nothing you enter is sent anywhere, and the step list shows the intermediate values so you can check the arithmetic by hand.
Every page in this section carries:
- the formula in full, with each variable named and its unit stated
- a step-by-step computation for the values currently in the inputs
- a sensitivity or range view showing how the answer moves when one input changes
- the assumptions the model holds fixed, stated explicitly rather than buried
- the source the formula is taken from, so the result can be checked against the original
Picking the right calculator
Start from the quantity you already know. Most tools here are reversible, so a payment calculator has a sibling that solves for the amount you can borrow at a payment you name.
Calculators sharing a name differ in what they hold constant — compare the assumptions section, not the title.
Where these tools stop
- Tax, benefits, fees, and eligibility rules vary by jurisdiction and year; a general tool cannot encode every local exception.
- Financial, medical, and legal outputs here are informational — a starting point for a professional, not a substitute.
- Where a figure depends on a changing rate, the page states the value it used and when it was set.
The market in the URL controls the numbers: currency, measurement convention, and any regional rule that changes the calculation. The interface language is a separate browser setting that never changes a result — it translates the labels while the computation, its units and its sources stay as they are.
Checking our work
Where a page states a standard, constant or regulatory limit, it names the source so the figure can be traced back. The methodology page describes how tools are generated and validated, rounding policy documents how displayed values are rounded, and sources and standards lists the references behind the platform. If a figure looks wrong, the corrections policy explains how to report it and what happens next.