Calculators built by hand, that show their work.
I’m Umer Farooq, and I built calcsdone around a simple idea: put the calculators people actually need — for finance, school, construction, and fitness — in one place, with the formula and logic behind every result visible instead of hidden. Nothing you type is ever sent to a server.
Browse the calculator library →Why I built this site
I kept running into the same problem: the calculator I needed either wanted an email address, buried the answer under three ad units, or wouldn’t tell me how it got to its number. So I started building my own, one at a time, and calcsdone is the result — a free collection with no sign-up and no results hidden behind advertisements.
Every tool here is meant to be simple enough to use in seconds, but transparent enough that you can check the math yourself.
Read our FAQ →Zero data collection
No sign-up, no tracking of what you input. Every calculator runs entirely in your browser.
Instant results
Results update as you type — no loading time, no API calls.
Verified formulas
Every calculator links its sources and methodology at the bottom of the page, drawn from authoritative references.
Always free
No paywalls, no usage caps, no premium tier.
Meet the founder
calcsdone isn’t run by an anonymous team — it’s built and maintained by one person, listed here so you know exactly who stands behind the numbers.
Umer Farooq
Founder & developer, calcsdone
I design, build, and maintain every calculator on this site myself. Each tool is checked against known worked examples before it goes live, and its formula is cross-referenced against the sources listed on that calculator’s page. If a formula or a standard changes, I update the page — you can see the “last updated” date on every calculator for that reason.
The principles behind every calculator
I check every formula against a standard reference before a calculator goes live, and again whenever I revisit the page.
Clarity first
Plain language throughout — no jargon you have to decode before you can use a result.
Show the formula
Every result is shown alongside the formula and steps that produced it.
Privacy by default
Nothing you type is tracked or stored — every calculation runs in your browser.
Built from requests
Most calculators on this site exist because a reader asked for them. If you’d like to see one that isn’t here yet, reach out through the contact page.
Same three steps, every time
Source the formula
Sourced from cited, industry-standard references. Results aren’t guesses — they’re calculated with the standard formula for that field.
Build and test it
Every calculator is checked against known worked examples before it goes live. If you spot a bug, please report it.
Publish, then refine
You can suggest changes to any calculator once it’s live, and I aim to review and apply reasonable suggestions quickly.
Have a calculator in mind?
Suggest a calculator and I’ll look at adding it within a few days.