US cups to milliliters converter

A recipe written in US cups may need conversion for a graduated jug or a set of measuring spoons. Fractions such as a quarter or three quarters of a cup are valid inputs. This is a US customary cup; a metric cup uses a different capacity.

One US cup is exactly 236.5882365 milliliters. The US customary cup is 8 US fluid ounces, exactly 236.5882365 mL.

Multiply the number of US cups by 236.5882365. For example, 1 cup × 236.5882365 = 236.588237 mL. To go the other way, divide by 236.5882365.

Multiply by 240. That is 1.4% high of the exact factor 236.5882365, so 1 cup comes out as 240 mL instead of 236.5882.

Both are in use. The US customary cup in recipes is 236.588 mL. US nutrition labels use a rounded "legal cup" of 240 mL (21 CFR 101.9), and the metric cup used in Australia, New Zealand and Canada is 250 mL.

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “1 cup to mL” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.