Unit Converter for iPhone & iPad. Version 1.0
Metron is a unit converter built for people who are paid to be right about numbers — STEM students, engineers and working scientists. It covers well over a hundred categories and more than twelve hundred units, and every one of them is free, forever.
What makes it different from a table of factors is the rigour around the number: significant figures, compound and derived units such as J/(mol·K), dimensional checking that refuses an impossible conversion instead of quietly returning a wrong answer, uncertainty carried correctly through a calculation, and the CODATA 2022 physical constants with their published uncertainties.
Every conversion runs on your device. Metron makes no network request of its own.
9.81 m/s^2 to ft/min^2, 2.5e-3 mol/L × 180 g/mol, h*c/(500 nm) to eV.Every factor in Metron is sourced, and the app will tell you which source, on any unit’s detail sheet:
Metron distinguishes a value that is exact by definition from one that is measured. 1 in ≡ 2.54 cm is true by fiat and will never change; the unified atomic mass unit is a measurement that has moved four times since 1986. The app marks which is which.
Every category, every unit and full-precision conversion are free forever, with or without Pro. We think paywalling a base SI unit is indefensible.
Pro adds the workflow around the numbers: the expression solver, significant figures and uncertainty propagation, molar mass from a chemical formula, unlimited history and favourites, export to CSV, LaTeX and Markdown, iCloud sync, and no ads.
Pro is available monthly or annually, with a 7-day free trial on the annual plan, or as a one-time Lifetime purchase. You can see, change or cancel your plan at any time under Settings › Membership, which also has a Restore Purchases button.
Because energy and force are different physical dimensions, and no factor relates them. Most converters would either hide the option or return a number anyway. Metron tells you why it cannot: “Cannot convert L² M T⁻² to L M T⁻² — the dimensions differ.” Catching that mistake is the point.
Whichever you pick. Metron never ships a bare “gallon”: it has US liquid, US dry and imperial gallons as separate units, avoirdupois and troy ounces, short, long and metric tons, thermochemical and IT calories, and so on. Confusing them is the most common real-world conversion error, so the app makes the choice explicit.
Because a rise of 1 °C is a rise of 1 K, not 274.15 K. Absolute temperatures and temperature differences convert by different rules, and an app with only one temperature category gets one of them wrong. Metron ships both.
No. The engine always works at full precision. The free tier limits how many significant digits are displayed, never what is computed.
Completely. Metron makes no network request of its own. The only network traffic in the free version belongs to the advertising SDK; Pro removes that too.
Please tell us, and say which unit and which source you are checking against. A wrong factor is the most serious bug this app can have and it will be fixed in the next build.
For support: mwsupplylimited@gmail.com
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