About Measure Owl
Measure Owl is a free unit converter for length, weight, volume, temperature, kitchen measures and time. Type a number, pick two units and the answer appears at once, together with the factor behind it, so you can check the math rather than trust a black box.
Why another converter
Most conversions people search for are small daily problems: ounces in a recipe, centimeters on a form, minutes turned into decimal hours for a timesheet. Measure Owl keeps each of them one tap away and prints the exact definition used, for example 1 inch = 25.4 mm and 1 pound = 0.45359237 kg.
Where the numbers come from
Factors for length, mass, volume and area follow the exact definitions of the International System of Units and the US customary units published by NIST. Cup-to-gram conversions are different: they use typical weights per cup for each ingredient and are marked as approximate. Flour, granulated sugar and packed brown sugar come from King Arthur Baking’s ingredient weight chart; butter uses 8 US ounces per cup and honey 16 tablespoons at 21 g each.
What we do not cover
- Currency rates, which change by the minute and are not units in the physical sense.
- Medical dosing. Do not use a converter alone for medicine; follow the label or ask a pharmacist.
- Legal or trade measurement. Use certified instruments when a contract demands it.
How the converter was tested
The Measure Owl team writes each converter. On 12 October 2026 we took every ordered pair of units in the length, mass, volume and area tables, 280 pairs in all, converted 100 of the first unit into the second and back again. The largest drift in any pair was 1.4 × 10⁻¹⁶ of the starting value, which is floating-point noise far below the eight digits shown. For example, 100 in becomes 2540 mm and returns as 100 in.
Temperature and time conversions use their own formulas and are checked against the landmarks printed on the home page, such as −40 °C = −40 °F. Anything that drifts is fixed or removed, and a page date changes only when its content does.
Contact and privacy
Corrections and unit requests go to the address on the contact page. Conversions run in your browser; see the privacy policy for the little we store and the terms of use for the rules.
Frequently asked questions
Who writes Measure Owl?
The Measure Owl editorial team. We cite standards instead of personal credentials.
Is it free?
Yes, with no account, fees or ads at the moment.
Can I rely on it for work?
For everyday tasks, yes. For regulated or safety-critical work, use certified tools and confirm with the governing standard.
Back to the Unit Converter on the home page.