--- title: "21 fl oz to cup = 2.625 cup" description: "21 US fluid ounces is 2.625 US cups. The arithmetic, a table of nearby values, and a converter for any other number." url: https://atoneplace.net/convert/21-fl-oz-to-cups/ site: "At One Place" --- # 21 fl oz to cup **21 US fluid ounces in US cups: 21 fl oz = 2.625 cup** cup = fl oz × 1/8 21 US fluid ounces is 2.625 US cups. To get there, multiply by 0.125. ## Values either side *US fluid ounces near 21, converted to US cups.* | US fluid ounces | US cups | | --- | --- | | 17 fl oz | 2.125 | | 18 fl oz | 2.25 | | 19 fl oz | 2.375 | | 20 fl oz | 2.5 | | 21 fl oz ← | 2.625 | | 22 fl oz | 2.75 | | 23 fl oz | 2.875 | | 24 fl oz | 3 | | 25 fl oz | 3.125 | ## How the conversion works The relationship is cup = fl oz × 1/8. Both units measure volume, so the conversion is a fixed factor that never changes. The figure is exact rather than approximate: since the international yard and pound agreement of 1959, an inch is defined as exactly 25.4 millimetres and a pound as exactly 0.45359237 kilograms, and every other imperial and US customary unit here is derived from those two. > US cup: US legal cup is 240 mL; the customary cup used here is 236.588 mL. ## Common questions ### What is 21 fl oz in US cups? 21 fl oz is 2.625 cup. ### How do you convert US fluid ounces to US cups? Multiply by 0.125. ## Related pages - [US fluid ounces to US cups](https://atoneplace.net/convert/fl-oz-to-cups/) - [21 cup to fl oz](https://atoneplace.net/convert/21-cups-to-fl-oz/) - [17 fl oz to cup](https://atoneplace.net/convert/17-fl-oz-to-cups/) - [18 fl oz to cup](https://atoneplace.net/convert/18-fl-oz-to-cups/) - [19 fl oz to cup](https://atoneplace.net/convert/19-fl-oz-to-cups/) - [20 fl oz to cup](https://atoneplace.net/convert/20-fl-oz-to-cups/) - [22 fl oz to cup](https://atoneplace.net/convert/22-fl-oz-to-cups/) - [23 fl oz to cup](https://atoneplace.net/convert/23-fl-oz-to-cups/) - [24 fl oz to cup](https://atoneplace.net/convert/24-fl-oz-to-cups/) - [25 fl oz to cup](https://atoneplace.net/convert/25-fl-oz-to-cups/) ## Sources - Guide for the Use of the International System of Units (SP 811) — NIST (https://www.nist.gov/pml/special-publication-811) [Public domain (US Government)] - The International System of Units (SI Brochure) — Bureau International des Poids et Mesures (https://www.bipm.org/en/publications/si-brochure) - Calculated on this page — At One Place (/about/)