All 13 calculators
Each one is free, needs no account, and runs entirely in your browser — nothing you type is sent anywhere.
Business & money
6Pricing, selling fees, VAT and what savings grow to.
Profit Calculator
Your real margin on eBay, Amazon and Shopify after every fee each one takes.
VAT Calculator
Add or remove VAT at 20%, 5% or a rate you set.
Compound Interest Calculator
What savings grow to, year by year, with the working shown.
Margin & Markup Calculator
Turn cost into price, or price into margin — without the platform fees.
Cost of Goods Sold Calculator
The whole statement — opening stock down to gross profit, line by line.
Invoice Generator
Build an invoice, proforma or quotation and download it as a PDF.
Maths
2Percentages and ratios, with the arithmetic shown.
Everyday
4Dates, worked hours, and converting units.
Age Calculator
Exact age in years, months and days — or the gap between any two dates.
Unit Converter
Length, weight, volume, temperature — and grams to cups, by ingredient.
Grams to Cups Converter
How many cups a weight comes to — for the ingredient you are actually using.
Hours Calculator
Add up worked hours between two times, across days or a whole week.
Health
1Body measurements, with the limitations stated.
Why another calculator site?
The working is shown
Every result comes with the arithmetic that produced it, using your own numbers. If you can’t follow it, we’ve failed.
The gaps are named
Each calculator says what it doesn’t model — VAT, fulfilment fees, returns. A tool that quietly overstates is worse than no tool.
Nothing that goes stale
No take-home pay, no stamp duty, no mortgage rules — anything that depends on a Budget is deliberately left out rather than left rotting. What is here is arithmetic, and arithmetic keeps.