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Free Online Unit & Currency Converters

Converters translate a value from one unit or currency into another using standard, verifiable formulas — SI-based conversion factors for physical units, and a public exchange-rate feed for currency. These are reference tools for everyday use, not a substitute for a financial-grade data feed on time-sensitive trades.

Converter tools

Unit Converter

Convert length, weight, temp, volume.

$

Currency Converter

Convert currencies with live rates.

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Age Calculator

Find exact age in years, months, and days.

%

Percentage Calculator

Find a percentage, increase/decrease, or add/subtract %.

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Grade Calculator

Calculate a weighted average grade.

Time Duration Calculator

Find elapsed time between two clock times.

Common uses

How to choose

The split between the two converters here is simple: the Unit Converter handles physical quantities — length, weight, temperature, and volume — using fixed conversion factors that never change (a mile is always 1.60934 kilometers). The Currency Converter is fundamentally different because exchange rates move constantly; it pulls from a public rate feed updated roughly daily, which is fine for budgeting a trip or estimating a purchase but not precise enough for time-sensitive trading or invoicing decisions where you need a live, licensed data feed. If you need to convert a recipe or a body measurement, use the Unit Converter; if you're converting money, treat the Currency Converter's output as a same-day estimate rather than an exact quote.

Both converters share the same design principle as the rest of the site: the math happens in your browser, so there's no delay waiting on a server round-trip for something as simple as converting inches to centimeters. The Currency Converter is the one exception that needs any network activity at all, since exchange rates by definition have to come from somewhere outside your device — everything else about the calculation, including rounding and display, happens locally.

Frequently asked questions

How often are currency exchange rates updated?

Rates are pulled from a public exchange-rate API roughly once a day — suitable for general reference, not real-time trading decisions.

Are unit conversions based on exact standard values?

Yes — length, weight, and volume conversions use standard SI-based conversion factors; temperature conversions correctly handle Celsius, Fahrenheit, and Kelvin's different zero points.

Further reading

Why Your Unit Conversion Doesn't Match: Rounding Errors Explained

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