Volume Converter

Volume converter that switches between liters, gallons, cups, milliliters, cubic meters, and more instantly. Free, private, runs in your browser, no signup.

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Last verified July 2026

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Direct answer

What does this converter do?

Volume converter that switches between liters, gallons, cups, milliliters, cubic meters, and more instantly. Free, private, runs in your browser, no signup.

  • 1 US gallon = 3.785 liter · 1 US cup = 236.6 milliliter · 1 US tablespoon = 14.79 milliliter
  • All conversions route through the liter as the base unit, so every pair of units agrees regardless of which two you enter.
  • Standard factors are shown in the formula panel at the precision the calculator actually uses, so the arithmetic and the panel agree.
Milliliters per cup across US, legal, metric, and imperial measures
Cup sizes differ by up to 5.7% against the 250 mL metric cup.

Reference factors (volume)

Exact factors in terms of the liter, from NIST standards:

  • 1 milliliter = 0.001 liter
  • 1 US teaspoon = 0.00492892 liter
  • 1 US tablespoon = 0.0147868 liter
  • 1 US cup = 0.236588 liter
  • 1 US quart = 0.946353 liter
  • 1 liter = 1 liter
  • 1 US gallon = 3.78541 liter
Formula & evidence

How this calculator works

Reviewed 2026-09-20 · BoringToolsKit Editorial Team

Formula

Volume = value x (litres per source unit) / (litres per target unit). Factors: 1 US gal = 3.785411784 L, 1 US qt = 0.946352946 L, 1 US cup = 0.2365882365 L, 1 US fl oz = 0.02957352956 L, 1 mL = 0.001 L.

Worked example

1 US gallon = 3.785 liter · 1 US cup = 236.6 milliliter · 1 US tablespoon = 14.79 milliliter

Sources

Sources support the method, terminology, or planning context. Editable assumptions remain your responsibility.

Assumptions to verify

  • Inputs are treated as exact decimal values.
  • Standard (not historical or survey) unit definitions are used.
  • The calculation uses the factors at the precision shown in the formula panel; rounding beyond that is display-only and adds no accuracy.

Frequently asked questions

Why convert through liter instead of directly?

Routing every unit through a single base (liter) means each unit needs only one exact factor against the standard, and any pair combines cleanly. Direct pair factors drift apart over time in hand-maintained tables; a base-unit graph cannot.

Where do these exact factors come from?

From published standards (NIST: SI units and US customary conversion tables). Units like the inch are defined exactly (1 in = 2.54 cm since 1959), so conversions between standard units are exact, not approximate.

How many decimal places should I trust?

The math is exact to the precision shown. The practical limit is your input: a tape measure is only good to ~1 mm and a kitchen scale to ~1 g, so 3–4 significant figures already exceeds the measurement's own accuracy.

Cite this tool

BoringToolsKit. “Volume Converter.” boringtoolskit.com/volume-converter/ (reviewed 2026-09-20). Free to reference in articles, syllabi, and answer posts with a link.

Privacy: Inputs and results stay in this browser. Conversion runs locally in your browser; review the output before relying on it.

Worked example: 2.5 gallons to cups

A gallon is defined as exactly 3.785411784 liters, and a cup is exactly 236.5882365 mL (one sixteenth of a gallon). Because both trace back to the same definition, 2.5 gallons converts to exactly 40 cups, with no rounding anywhere in the chain: 2.5 x 16 = 40. The liters figure is 2.5 x 3.785411784 = 9.46352946 L, and the tool rounds that display to 9.46.

In fluid ounces the same input gives 2.5 x 128 = 320 fl oz. Notice the practical pattern: since 1 gallon = 4 quarts = 16 cups = 128 fl oz, you can move between these US kitchen units without ever touching the liter value. Enter 2.5, pick US gallons as the source, then switch the target between cups, quarts, and fluid ounces to see 40, 10, and 320 instantly. The milliliter row shows where rounding starts: 9463.5 mL displays as 9,464 because the formatter drops to whole units at 1,000 and above.

US vs imperial: where 20% bites

US and imperial gallons differ by about 20%: the imperial gallon is exactly 4.54609 L versus 3.785411784 L for the US gallon. Pour a UK-recipe 'gallon' into a US-measured container and you are short 0.7607 L, roughly 3.2 US cups. The same trap runs through smaller units: an imperial fluid ounce is 28.4131 mL while the US fluid ounce is 29.5735 mL, so 16 imperial fl oz is about 0.83 US pints, not one.

Cooking adds a second gap: a US legal cup (240 mL, used on nutrition labels) differs from the converter's 236.5882365 mL customary cup by about 1.4%, and the metric cup common in Australian and Canadian recipes is 250 mL, about 5.7% more. For a single cup of stock that is noise. For a 16-cup batch of brine it is almost a full cup of error, which is why the source units matter more than the decimal places.