What is a multi-currency calculator?

A multi-currency calculator lets you mix several currencies inside a single arithmetic expression. Instead of converting each amount in a separate tool, you tag individual numbers with a currency code and the calculator converts them on the fly using live exchange rates before computing the total. The BigIdeasDB Multi-Currency Calculator is the first web calculator built around this expression-style workflow.

How is this different from a normal currency converter?

Normal converters operate on one amount at a time: amount in, amount out. This calculator evaluates an entire arithmetic expression that can contain numbers in many different currencies. Type 1 + 1(USD) + 2 and you get a single total in your home currency, with each conversion shown transparently.

How do I tag a number with a currency?

Two formats are supported. A 3-letter code after the number, such as 50 USD or 50usd. Or the code in parentheses, such as 1(USD). Untagged numbers automatically use your selected home currency.

Is the BigIdeasDB Currency Calculator free?

Yes. The BigIdeasDB Multi-Currency Calculator is 100% free, requires no signup, and runs entirely in your browser. Exchange rates are fetched from a public open exchange feed and cached for one hour.

Where do the exchange rates come from?

Live rates come from the open.er-api.com public feed, which aggregates data from multiple sources. Historical chart data is sourced from Frankfurter, an open API backed by European Central Bank reference rates. The calculator displays the timestamp of the last update so you can verify how fresh the rates are.

Does the calculator store my data?

Only in your own browser. Your recent expressions and selected home currency are saved to localStorage so they persist between sessions. Nothing is sent to a server. You can clear history at any time from inside the calculator.

Can I see historical rates?

Yes. The rates panel includes a live chart that shows the historical exchange rate between any popular currency and your home currency, with 7-day, 30-day, 90-day, and 1-year views.

Is there a calculator keypad for clicking instead of typing?

Yes. Click the Show keypad button under the expression input. You get a numeric keypad, operator keys, parentheses, and one-tap currency tag chips so you can tag a number with a currency without typing the code.

Which currencies are supported?

USD, CAD, EUR, GBP, JPY, AUD, CHF, CNY, INR, MXN, BRL, ZAR, SEK, NOK, DKK, NZD, SGD, HKD, KRW, PLN, TRY, RUB, AED, SAR, THB, IDR, MYR, PHP, ILS, CZK, HUF, RON, CLP, COP, ARS, PKR, VND, EGP, NGN, and TWD — 40+ currencies in total.

Who is this calculator for?

Anyone whose money math crosses borders: freelancers paid in one currency but spending in another, travelers budgeting across countries, online shoppers stacking foreign product prices with local taxes, investors and traders holding assets across exchanges, and remote teams splitting costs across currencies.

Is there an open-source or self-hosted version?

The calculator runs as a free web tool at bigideasdb.com/currency-calculator. There is currently no separate self-hosted distribution; the goal is a single, always-up-to-date web experience.

Does it work offline?

Once rates are loaded, the math is computed entirely in your browser, so you can keep working briefly without a network. A fresh page load needs network access to fetch the latest exchange rates.

A new kind of calculator · 100% Free

The first web calculator that mixes currencies in one expression.

Type 1 + 1(USD) + 2 and get a single live total in your home currency. Live rates, historical charts, expression history, and an optional keypad — built for anyone whose money math crosses borders.

What makes it different

A money math workspace, not just a converter

One expression, mixed currencies

Tag any number with a currency like 1(USD) or 50 cad. Everything else uses your home currency.

Live exchange rates

Rates pulled from a reputable open exchange feed and refreshed every hour.

Live rates table & charts

See every popular currency vs your home, with 7D / 30D / 90D / 1Y historical trend lines.

Local expression history

Recent expressions are saved in your browser. Click any past expression to restore it instantly.

Optional calculator keypad

Prefer to click? Toggle the on-screen keypad with one-tap currency chips for fast tagging.

Transparent math

See each tagged amount converted, the rate used, and when rates were last updated.

Who this is for

Anyone whose money math involves more than one currency

Freelancers

Get paid in USD but spend in CAD. Add an invoice and a few CAD expenses in one expression.

Travelers

Budget a trip across three countries without switching apps for every total.

Online shoppers

Stack a USD-priced product, a EUR shipping fee, and your local tax into one final number.

Investors & traders

Mix USD-listed stocks, EUR dividends, and local-currency fees in one running total.

A novel solution to a real, everyday problem

Most online currency tools are converters: amount in, amount out. That works when you have one number. It falls apart the moment your math crosses borders — a USD invoice, a EUR subscription, a CAD coffee — and you want a single total in your home currency.

The BigIdeasDB Multi-Currency Calculator is, to our knowledge, the first web calculator built around this exact workflow. Native apps like Numi and Soulver have hinted at the idea on macOS, but no browser-based tool has shipped a clean, expression-style mixed-currency calculator. Until now. Set your home currency once, write a normal arithmetic expression, and tag any number with a currency code. The calculator converts tagged amounts on the fly using live exchange rates, then evaluates the whole expression in your home currency.

Example expressions you can paste right now

1 + 1(USD) + 2 — one tagged USD amount, the rest in your home currency
50 cad + 10 usd - 4 eur — three different currencies in one line
200 + 30 usd * 1.13 — apply tax on a USD amount, then add a local total
(1200 + 40 usd + 20 usd) / 3 — split a mixed-currency bill across three people
2500 usd - 80 eur - 35 gbp — a freelancer's monthly net across providers and fees
100 * 47.20 usd — a 100-share US stock position in your home currency

How tagging works

You can tag a number two ways: a bare 3-letter code immediately after the number (50 USD or 50usd), or the code in parentheses (1(USD)). Any untagged number uses the home currency you selected in the calculator. The total is always returned in the home currency.

Live rates, historical charts, and a real workspace

Below the calculator, you'll find a live rates panel that shows every popular currency relative to your home currency, plus an interactive chart with 7-day, 30-day, 90-day, and 1-year ranges. Live rates come from a public open exchange feed and refresh every hour. Historical data comes from Frankfurter, an open API backed by European Central Bank reference rates. Every conversion in the calculator surfaces the exact rate it used and the timestamp it was last refreshed, so you can always verify the math.

Built for keyboards, mice, and phones

The fastest input path is typing — but you can also flip on the on-screen keypad. The keypad gives you numeric keys, operators, parentheses, and one-tap currency tag chips, so you can build expressions without remembering codes. Recent expressions are saved locally in your browser; click any past expression to restore it instantly. Nothing leaves your device.

Why it matters

The internet's currency calculators were designed for a world where you converted one number at a time. The world has changed. Software is global, hiring is remote, shopping is cross-border, and most balance sheets touch at least two currencies. The BigIdeasDB Multi-Currency Calculator gives the web a single place to do that math — quickly, transparently, and for free.

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