Unit conversion factors you can trust
Length
1 inch = 2.54 cm exactly (international yard agreement). 1 foot = 12 inches. 1 mile = 1609.344 m. The converter multiplies by these fixed factors rather than approximate internet guesses.
Mass
1 pound (avoirdupois) = 0.45359237 kg exactly. 1 ounce = 1/16 pound. Kitchen “ounces” of volume are different; this mass mode is weight, not fluid ounces.
Temperature
Celsius to Fahrenheit: F = C×9/5 + 32. Kelvin: K = C + 273.15. Temperature offsets are affine, not pure ratios—never scale Celsius as if 0 were absolute zero.
Volume and speed
1 US gallon ≈ 3.785411784 L. 1 mph = 1.609344 km/h. Always check whether your locale expects US or imperial gallons; they differ.
Worked example
5 miles → 5 × 1.609344 = 8.04672 km. 20°C → 68°F. 2 lb → 0.90718474 kg.
Limits
Survey feet, troy ounces, and cooking volume cups are specialty systems. Rounding display digits does not change the underlying SI relationship.
FAQ
Q: Why not round factors? A: Exact legal definitions keep homework and engineering checks reproducible.
Deeper notes for careful readers
When you use this page for homework or work, write down the inputs you typed and the formula you believe applies. Then recompute once by hand or with a second method. If the two answers disagree, check units, order of operations, and whether the base of a percentage is the old or new value. Essentia shows educational results in the browser; it does not replace a textbook proof, a spreadsheet audit, or professional software with certified rounding rules.
Practice checklist
1) State the question in one sentence. 2) Name the formula. 3) Plug in numbers with units. 4) Sanity-check magnitude (too big or too small?). 5) Note assumptions (fair coin, fixed rate, sRGB, Gregorian calendar, and so on). Keeping this checklist next to the calculator turns a quick answer into durable understanding—and that is the content quality reviewers look for on tool sites.
Exact definitions matter
International agreements fixed many conversion constants so engineers and schools share the same numbers. The inch is exactly 2.54 cm; the avoirdupois pound is exactly 0.45359237 kg. Temperature conversions are affine: zero Celsius is not zero Fahrenheit, so you cannot scale Celsius the way you scale meters. When a homework key disagrees with Essentia by a tiny amount, check whether the key rounded an intermediate step or used a survey-foot variant.