Cooking numbers and lab numbers are different sports
Length, mass, area, and volume here are multiply-by-a-factor conversions. Temperature is not. Celsius to Fahrenheit is × 9/5 + 32. People still “convert” 100°C to 100°F in their heads because the labels look like the same kind of unit. They are not. I special-case C, F, and K so a kitchen thermometer and a chemistry homework set do not share a broken linear path.
The gallon in the volume list is the US gallon (3.78541 L), not the imperial gallon (4.54609 L). If your recipe is from a UK book that says “pint,” stop: a UK pint is 568 ml, a US pint is 473 ml, and this page does not list pints or cups. Cups are missing on purpose. A US legal cup is volume. A “cup of flour” in a bakery is mass. Density is not modeled. Using a volume converter to scale a cake is how you get soup.
Worked example: 72°F to Celsius
From F to C: (72 − 32) × 5/9 = 22.222…°C. Room-ish. Oven copy that says 180°C is about 356°F, not 180 × 2. If you need Kelvin for a lab write-up, 22.222°C is 295.37 K (add 273.15). Do not report twelve decimal places of JavaScript float as if you owned a platinum resistance thermometer.
Worked example: 250 g of something to ounces
Mass family: 250 × 0.001 / 0.0283495 ≈ 8.82 oz. Fine for a shipping label. Not a cup of flour. All-purpose flour is roughly 120–130 g per US cup depending on scoop vs spoon. If a US blog said “1 cup (250 g) sugar,” that is a different density than flour. Convert mass to mass. Convert volume to volume. Cross them only with a density you are willing to defend.
Worked example: 5 km to miles
5 × 1000 / 1609.34 ≈ 3.107 miles. Good enough for a Sunday run. A surveyor would care about the international mile vs US survey foot history; this page uses 1609.34 m per mile and 0.3048 m per foot, which is what homework expects. Acres and hectares sit in area, not length. Square the conversion if you are going m² to ft²; do not take a length factor and call it area.
Precision, and what I will not add
IEEE floats. Displaying 8.81849 oz is not a calibration certificate. Significant figures are your job. Currency is not a unit here; FX belongs in a rate table with a timestamp, which this file does not fetch. Scientific constants, cooking “sticks of butter,” and Troy ounces for gold are out. Custom units are out. If you need SI prefixes beyond what is listed (ng, Mm), write the factor on paper. For percent change, use the percentage calculator, not a fake “unit.”
Kitchen fails I see on purpose: converting 180°C ovens with a factor of 2; treating 250 ml as 250 g for everything denser or lighter than water; mixing US fluid ounces (volume) with ounces mass. The lists are separate families. If the dropdown still shows kg after you switched the type to length, change the type first so the unit menus rebuild. Lab fails: reporting Kelvin with a degree sign, or assuming 1 L of a reagent is 1 kg. Water is close. Ethanol is not. This page will not save a titration.
Questions
Is temperature converted like length?
No. C, F, and K use the usual formulas. 0°C is 32°F, not 0°F. Length uses factors to metres.
US gallon or imperial?
US (3.78541 L). Imperial gallons are larger. This list does not include UK pints or cups.
Why no cups?
A cup of flour is mass in the kitchen and volume on a measuring jug. Density is not modeled. Convert grams or millilitres, not “cups.”
Is this lab-grade?
No. Homework and cooking estimates. JavaScript floats, listed factors only. Not a metrology lab.
Currency?
Not this tool. Exchange rates need a timestamped table. Google Search is fine for FX.
Are my numbers uploaded?
No. Two dropdowns and a value stay in this tab. No account.