omacusConvert currencies as you type
Write an amount and where you want it, like $30 in EUR or £250 in USD. Omacus fetches exchange rates for 160+ currencies, keeps them on your computer, and answers on the same line.
Omacus is a free notepad calculator for Linux, macOS and Windows. Because money is just another unit to it, you can add, split and convert prices in the same line, and keep a whole trip's or invoice's worth of math on one page.
Quick examples
| You type | Omacus shows |
|---|---|
$30 in EUR | 26.75 EUR |
£250 in USD | $331.54 |
€50 + £20 in USD | $82.60 |
¥10,000 in USD | $63.26 |
100 USD to GBP | 75.41 GBP |
50 AUD in NZD | 61.57 NZD |
10k MXN in USD | $541.79 |
₹5,000 in USD | $52.58 |
Rates as of 16 October 2026. In the app you always get the latest rates.
Symbols or codes
Use the symbol you'd write by hand, $ £ € ¥ ₹ ₩ ₽ ₺, or any three-letter currency code, before or after the number: $30, 30 USD and USD 30 are the same. Thousands separators like $1,299 or ₹1,50,000 are fine, and k means thousands.
Convert with in or to. Results in dollars are shown as $; other currencies keep their code so it's always clear which one you're looking at.
Mixing currencies
Add amounts in different currencies directly. The answer comes back in the first currency on the line, unless you ask for another one:
| You type | Omacus shows |
|---|---|
£45 + $20 | £60.08 |
€50 + £20 in USD | $82.60 |
$12.99 * 3 in CAD | 55.30 CAD |
CHF 300 + EUR 50 in GBP | 315.40 GBP |
Everyday money math
Multiply, split, take percentages and work with rates like dollars per hour. Omacus keeps track of the units, so $85/hour * 160 hours is money, not hours.
| You type | Omacus shows |
|---|---|
$4.50 + $3.25 + $12 | $19.75 |
€1,200 / 4 | 300 EUR |
20% of €80 | 16 EUR |
$2,000 - 15% | $1,700 |
$85/hour * 160 hours in EUR | 12,126.44 EUR |
€50,000 + 20% VAT | 60,000 EUR |
Rates, and working offline
Omacus downloads exchange rates for 160+ currencies from a free public source when it starts, and saves them on your computer. They're refreshed every 12 hours while you're online. On a plane or without Wi-Fi, currency math keeps working with the last rates it saved. Nothing about you or your sheets is sent anywhere; the request only asks for the latest rates.
A trip, split four ways
Flights in dollars, everything else in yen, split per person, then shown in euros and pounds for friends back home:
- # Kyoto in autumn
- // 4 friends, 5 nights
- Flights: 4 * $1,180$4,720
- Ryokan: 5 nights * ¥68,000340,000 JPY
- Rail passes 4 * ¥50,000200,000 JPY
- Dinners ¥14,000 * 4 * 5280,000 JPY
- total$9,907.02
- each = prev / 4$2,476.75
- each in EUR2,208.40 EUR
- each in GBP1,867.60 GBP
- Lands 4:10pm JST in San Francisco12:10 AM PDT
- Call home 8pm JST in New York7:00 AM EDT
Questions
How many currencies does Omacus support?
More than 160, covering every currency with a published exchange rate from its rate source, from USD, EUR and JPY to smaller ones like NPR and KES.
Where do the exchange rates come from?
From open.er-api.com, a free exchange rate service. They're cached on your computer and refreshed every 12 hours.
Does currency conversion work offline?
Yes, using the last rates that were saved. You only need a connection to refresh them.
Can I add amounts in different currencies?
Yes. €50 + £20 in USD converts both and adds them. Without in, the answer is in the first currency on the line.
Does it support crypto like Bitcoin?
Not yet. Only government currencies are included for now.