Ten single-purpose converters with US units first, the formula shown, and no sign-up: speed, area, volume, pressure, energy, power, cooking measurements, fuel economy, shoe sizes and angles. Type a value — the answer is already there.
ConvertKit is the unit-conversion corner of the TapeToolHQ network. It deliberately covers the converters our general tool site does not: the everyday pairs people actually search for, from an mph to kmh converter for road trips to a cups to grams converter for baking. Every tool runs entirely in your browser, answers as you type, shows the exact conversion factor it used, and keeps easily confused units — US vs imperial gallons, mechanical hp vs metric PS — clearly labeled and separate.
All factors are standard exact definitions (NIST): 1 mile = 1.609344 km, 1 US gallon = 3.785411784 liters, 1 acre = 43,560 square feet, 1 kcal = 4,184 joules.
No. One US gallon is exactly 3.785 liters, while one imperial (UK) gallon is 4.546 liters — about 20% larger. ConvertKit always labels the two gallons separately so they are never mixed up.
Miles per gallon measures distance per unit of fuel, so a bigger number is better. Liters per 100 km measures fuel per unit of distance, so a smaller number is better. The two are reciprocals: L/100km = 235.215 ÷ mpg (US), and 282.481 ÷ mpg (imperial).
Mechanical horsepower (hp) is 745.7 watts. Metric horsepower (PS), common in European car listings, is 735.5 watts. They are close but not identical, so ConvertKit lists them as separate units.
A cup measures volume, not weight, and ingredients pack differently. A cup of all-purpose flour weighs about 120 grams, while a cup of granulated sugar weighs about 198 grams. That is why the cooking converter asks which ingredient you mean before giving grams.