Free · Unit conversions

Five-Mode Metric & Customary Unit Converter

Convert length, area, volume, mass and absolute temperature using paired unit selectors and reversible results.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

One foot equals 0.3048 m, one pound equals 0.45359237 kg, and one US gallon equals 3.785411784 L. Zero degrees Celsius equals 32 °F or 273.15 K.

Apply the selected unit scale; °F = °C × 9/5 + 32; K = °C + 273.15

Worked example

Enter these known values and leave the other values blank.

Length in metric units
.3048 m
Length in imperial units
1 ft

Assumptions and limitations

  • US customary and UK imperial volume units differ. The default gallon is the US liquid gallon; use the selector to identify the intended unit.
  • Temperature mode converts absolute scale readings, not temperature differences. Its offset formulas must not be applied to a change in temperature.
  • Mass mode converts units of mass. It does not convert mass into gravitational force or require an assumed local gravity.
  • Switching the quantity type preserves values in the other modes. Each mode is independent.

Common questions

Can I enter the customary value first?

Yes. Enter either side of the selected conversion; the captured inverse relation computes the other side.

References

Bookify rejects absolute temperatures below zero kelvin. The international acre is exactly 43560 square international feet; Bookify replaces the rounded captured area factor. The US dry gallon uses one eighth of a 2150.42-cubic-inch bushel, replacing the rounded captured volume factor. The cubic international mile uses the cube of the exact 1609.344-meter mile, replacing a rounded reciprocal factor. The US fluid ounce uses one 128th of the exact US liquid gallon, replacing the rounded captured reciprocal factor. The US customary cup uses one sixteenth of the exact US liquid gallon, replacing the rounded captured cup volume. Bookify replaces the captured rounded US gallon with the exact 3.785411784-liter definition.

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