Unit Converter for Length, Weight, and Volume

Worked examples

How the cups to milliliters conversion works

Volume conversions are pure multiplication. One cup equals a fixed number of milliliters, so the milliliters you want is simply your quantity of cups multiplied by that fixed number.

For example, if one cup is 236.588 mL, then 2 cups is 2 times 236.588, and half a cup is 0.5 times 236.588. There is nothing to estimate — the factor is exact by definition once you pick which cup standard you mean.

• Cups to mL: multiply cups by mL-per-cup.
• mL to cups: divide mL by mL-per-cup.
• Doubling the cups doubles the milliliters — the relationship is linear.

Which cup should you use?

The word cup means slightly different volumes in different places, and picking the wrong one is the single biggest source of error.

Use the US customary cup (236.588 mL) for most American recipes, the US legal cup (240 mL) when following nutrition labels or FDA-style measures, and the metric cup (250 mL) for recipes from Australia, New Zealand, and much of the Commonwealth.

• US customary cup: 236.588 mL.
• US legal cup: 240 mL (nutrition labeling).
• Metric cup: 250 mL.
• Imperial cup (older UK): about 284 mL — enter it manually if needed.

Using this tool for length and weight too

This calculator multiplies your value by whatever conversion factor you enter, so it is not limited to cups. Set the factor to the number of target units in one source unit and it converts anything.

For length, one inch is 25.4 mm, one mile is 1.609344 km, and one foot is 0.3048 m. For weight, one pound is 0.45359237 kg, one ounce is 28.349523 g, and one kilogram is 2.2046226 pounds.

• Inches to millimeters: factor 25.4.
• Pounds to kilograms: factor 0.45359237.
• Fluid ounces to milliliters (US): factor 29.5735.
• Liters to US cups: factor about 4.2268.

What changes the answer most

The conversion factor dominates the result. A small change in which cup standard you choose shifts the outcome by several percent, which matters in baking where ratios are tight.

Rounding is the other factor. Keep a few decimal places during the calculation and only round the final answer, so small errors do not accumulate across multiple conversions.

• Cup standard: 236.588 vs 250 mL is a 5.6% difference.
• Rounding early can drift the result over several steps.
• Decimals shown here control display only, not the internal precision.

Common mistakes to avoid

People often mix dry and liquid cups, but a US cup is the same volume for both — the difference is only in how you fill and level dry ingredients, not in the unit itself.

Another trap is converting weight to volume directly. Cups measure volume and grams measure weight, so you cannot convert one to the other without knowing the ingredient's density. This tool converts within volume, within weight, or within length — not across those categories.

• A cup of flour and a cup of water are the same volume, not the same weight.
• Do not convert cups to grams without a density figure.
• Match your factor's direction: mL-per-cup for cups to mL, not the reverse.

What this assumes

• Conversion is a single multiplication by a fixed factor you supply.
• One US customary cup equals 236.588 mL by default; change the factor for other cups or units.
• Weight and volume cannot be converted to each other without a density value.
• Displayed decimals affect only the shown result, not internal precision.