Type in plain language. Every line resolves as you go — units, currencies, percentages, variables, running totals. No formulas, no cells, no cloud.
Nothing leaves your browser. No sign-up. No tracking. Works offline.
Reckon parses real language into real math — with a dimensional engine that knows metres aren't seconds and dollars aren't degrees.
Write it how you'd say it. Words become operators.
$1,499 minus 20%
Length, mass, time, data, temperature, speed — converted and cancelled correctly.
60 mph * 2 hours in miles
150+ currencies with symbols. Live exchange rates on Pro.
12 GBP + 40 EUR in USD
Name a value once; reuse it below. sum above totals the block.
rent = $1,800
Add days to today, subtract dates, measure spans in any unit.
today + 3 weeks
sqrt, round, min/max, sin/cos, log, factorial — unit-aware where it counts.
sqrt(144) + 3^2
Reckon has its own little language — built from scratch, no libraries. That's what makes the natural phrasing and the unit safety possible.
A hand-written lexer and precedence-climbing parser turn your sentence into an expression tree — currency symbols, magnitude words, factorials and all.
Every value carries a dimension signature. Multiply metres by metres and you get area; add metres to seconds and Reckon tells you it can't.
Variables flow downward, so one edit re-runs the page top-to-bottom in a single linear pass. It feels instant because it is.
The whole calculator is free. Pro adds live rates, unlimited notes, and export — a single payment, no subscription.
.txtReckon is a static site. There is no server to send your salary, your runway, or your recipe to — because there is no server at all.
Yes. The entire calculating engine — every unit, currency, function, and variable — is free with no account. Pro is a one-time $19 that adds live exchange rates, unlimited notes, and export. No subscription, ever.
Pro is verified directly on-chain. You send a one-time payment in ETH — on Base, an Ethereum L2 where fees are under a cent and transfers confirm in seconds (Coinbase withdraws to it directly), or on Ethereum mainnet — paste the transaction, or let Reckon find it, and it's confirmed in your browser. No processor, no middleman, nothing stored about you.
In your browser's local storage, on your device. They're never sent anywhere. Clear your browser data and they're gone — so export anything important (Pro).
The calculator runs entirely client-side, so once the page has loaded it keeps working with no connection. Only live exchange rates need the network.
It's a calculating notepad, not a spreadsheet — there are no cells, charts, or macros. If you want fast answers to everyday math in plain language, that's exactly the point.
Open a page. Start typing. Watch it reckon.
Open Reckon — free →