Every currency. Always current.
More than 160 currencies and the major cryptos, with rates that refresh on their own. Mix dollars, euros and pounds in one line.
Write it down.
It adds up.
A notepad that calculates as you type. Currencies, units, dates and time zones, answered instantly.
Free for 7 days · No account, no card
Try me
160+ currencies
Crypto
150+ units
Time zones
TerminalWorks offline
Private by design
Write it the way
you would say it
Splitting the bill, checking a quote, planning a trip. Write a line and the answer appears beside it.
Any unit. Any time zone.
Kilometers to miles, Fahrenheit to Celsius. Ask what 3pm is in Tokyo, or how many days are left until the deadline.
The details
that add up
Every number stays on the page, and every answer is one glance away.
amortize €300k at 4.5% for 25 years€1,667.50300 payments of 1,667.50
interest 200,249.23
interest 200,249.23
Shows its working
Hover an answer to see how it got there: the rate, the conversion, each deduction.
L1price = 420420
L2tax = 8.5%8.5%
L3L1 + tax455.70
Line references
Write L3 to reuse a result. Change it once, and every line below follows.
Lists and plots
Sum a list, find the average or median, or draw sin(x) right on the page.
6d 20h 14muntil Friday 18:00
Live countdowns
Type "until 18:00" or "until Christmas", then watch the time tick away.
14 themes
Light, dark and in between, with glass and frosted looks on the Mac.
~ % ratio "5 km in mi"
3.11 mi
In your Terminal
On the Mac, type ratio "5 km in mi" in Terminal. Same engine, same answer.
AI
Just ask, in plain words
- Ask in plain words, get lines you can edit
- Runs on the model built into macOS
- Nothing you write leaves your Mac
# split a 120 eur dinner with a 10% tip between 4
bill = 120 eur€120
amount = bill + 10%€132
amount / 4€33
how much is that in usd?Ask AI
Notch
A calculator in the notch
- Opens when the pointer rests on the notch
- Or press ⌥⇧Space from any app
- Pin any line to the menu bar
Widgets
Your numbers, on the desktop
- “Days until payday” as a ring on your desktop
- The rate you check every day, with its last days as a chart
- What you pay each month, split by service
Money
Salary, mortgage and pension, worked out
- Take-home pay for Romania, Germany, the UK and the US
- Loans, savings, ROI and your FIRE number
- Invoices, VAT and working days
Math
Homework, solved
- Equations, integrals and derivatives
- Exact answers like 2√2
- Constants, units, statistics and primes built in
Developers
Subnets, hashes and the cloud bill
- CIDR ranges, masks and subnets
- Base64, SHA-256 and UUIDs
- Hex, binary and bit shifts
MCP
Claude asks, Ratio works it out
- Works with Claude, Cursor and VS Code
- Today's exchange rates, stocks and working days
- Set up with one command
Split 184 euros between 3 people, in dollars.
ratio calculate 184 eur / 3 in usd $68.55
That's $68.55 each, at today's rate of 1 EUR = 1.12 USD.
Share
Send the whole sheet as a link
- Opens in any browser, no app needed
- Logos, charts and colours come along
- The sheet lives in the link, not on our server
Same dinner bill.
Only one shows its work.
Drag the handle to compare a regular calculator with Ratio.
Calculator
One number, no history
Ratio
# dinner for 4
bill = 120 eur€120
tip = 10%10%
total = bill + tip€132
each = total / 4€33
each in usd$36.96
Every step kept, change any line
Private by design
Your numbers stay yours.
Ratio does every calculation on your computer. Nothing you type is sent anywhere, and it works offline.
Nothing leaves your computer.
Buy it once.
It's yours.
One version, with everything included. Use it free for 7 days. If you love it, buy it once and keep it for good.
2 computersPopular
$7.50 each. Your laptop and your desktop.
3 computersSave 33%
$6.66 each. Enough for the whole household.
Everything included, on every plan
- 160+ currencies
- Crypto
- 150+ units
- Time zones
- Live countdowns
- Line references
- Lists and plots
- Salary and loans
- Ask AI on your Mac
- Calculator in the notch
- In your Terminal
- MCP for Claude
- 14 themes
- iCloud sync
- Works offline
“Ratio makes everyday math feel effortless: just write things down and get clear, live answers instantly—no spreadsheets, no fuss. It handles currencies, units, dates, and more, all in one simple, private notepad. Loved it so much went back and got a couple more copies.”
Terry CarsonDeveloperMac, Windows and Linux · 14-day refund
Student or teacher? Half price. Write to us from your school email and we'll send you a code.
Questions
Ask AI about Ratio: ChatGPTClaudePerplexity
What is Ratio?
Ratio is a notepad calculator for Mac, Windows and Linux. You type calculations as plain text, like "dinner 84 eur / 3", and the answer appears beside each line as you type. It understands currencies, crypto, units, dates and time zones.
Does Ratio run on Windows and Linux?
Yes. Ratio runs on Windows 10 and 11 (64-bit) and on 64-bit Linux (Ubuntu 22.04 or newer, Debian, Fedora and others, as an AppImage or a .deb). It uses the same engine as on the Mac, so every line gives the same answer. The trial and the license work the same way everywhere, and a 2- or 3-computer license can mix a Mac, a PC and a Linux machine. iCloud sync, Liquid Glass and the Terminal command are Mac only for now.
Can Claude or other AI assistants use Ratio?
Yes, on the Mac. Ratio comes with an MCP server, so Claude, Cursor and VS Code can work out currencies, stock prices, units, dates and VAT with Ratio instead of guessing. How to set it up
Does Ratio work offline?
Yes. Every calculation happens on your computer. Exchange rates need a connection to refresh, and while you're offline, Ratio uses the last rates it downloaded.
Do I really pay only once?
Yes. You pay once, and that's it. Updates are included.
Is there a free trial?
Yes. Ratio is free for 7 days, with no account and no card. If you buy it and it isn't for you, email us within 14 days and we'll refund it.
How do I move my license to another computer?
In the app, open Ratio Pro and click “Deactivate this Mac” (or “Deactivate this PC” on Windows and Linux). Then enter the same key on the new computer, whether it's a Mac, a PC or a Linux machine.
See how it
all adds up
Try it free for 7 days. No account needed.
