How Numora tools are built and maintained

Last updated: 21 October 2026

This page explains what you can expect from a Numora calculator, how the numbers are produced and what you should not expect.

Formulas are shown, not hidden

Each tool page includes the formula behind the calculation and a worked example. You can repeat the example by hand or in a spreadsheet and compare it with the result. When a formula has variants, the page states which one the tool uses: the calorie estimate, for instance, uses the Mifflin-St Jeor equation with the activity factors listed in the form.

How a tool is built

Every calculator is a self-contained script that runs in the browser. The form checks that the inputs are usable before calculating: a length cannot be negative, a divisor cannot be zero and a date must be a real date. If an input is invalid, the tool shows a clear message instead of a misleading number. Nothing you type is sent to the server.

Calculation and rounding

• Calculations use standard JavaScript numbers and the standard formula printed on the page.
• Money results are shown with two decimals. Other results show up to eight decimals, and unit conversions up to six.
• Rounding happens only when a result is displayed, not during the calculation, so intermediate steps keep their precision.
• Large and small results are shown in a readable form, with thousands separators and without unnecessary trailing zeros.

Values that change over time

Exchange rates, VAT and sales tax rates and similar figures change often. Numora does not guess them: you enter the rate, so the result matches the source you trust. This also means the site cannot confirm that the rate you used is current; check it with an official source before relying on a total.

How results are checked

Each tool is tested with a worked example whose result can be verified independently. For finance tools the example is built from the same formula the page prints, so the arithmetic can be repeated line by line. For health tools the example follows the published equation and states the assumptions. For converters, the factors are the standard defined values, such as 2.54 centimetres per inch or 1,073,741,824 bytes per gibibyte.

Guides and editorial content

The guides explain concepts in plain English, with numerical examples that you can check using the linked tools. They follow the same rule as the tool pages: show the working, state the assumptions and avoid claims that cannot be verified. Guides are general information, not professional advice.

What the site does not do

• It does not provide personalised financial, tax, legal, medical or nutritional advice.
• It does not fetch live exchange rates or official tax rates; those values come from you.
• Financial results do not include fees, taxes or inflation unless the page says so.
• Date tools do not know local public holidays.
• It does not guarantee that a result is free of error or suitable for a particular purpose.

The tools are designed to support a decision, not to make it. For anything important, verify the figures with a qualified professional or an official source.

Advertising and independence

Numora may show advertising to cover its costs. Advertising does not change how a calculation works, which formula is used or what a guide says.

Corrections and updates

If you find an error, email trynumora@gmail.com with the tool name, the values you entered and the result you expected. Reports are checked against the formula and the worked example; confirmed errors are fixed and the affected page is updated. The date at the top of this page shows when the policy was last reviewed.