One US cooking cup equals 236.588 mL; nutrition labels round that to a 240 mL “legal cup.”
Here’s the short, precise answer people reach for during a recipe or a coffee-gear setup: a standard American measuring cup holds 236.588 milliliters by definition, and US nutrition labels treat a cup as exactly 240 milliliters. That tiny gap shows up when you compare cookbooks to packages, so this guide shows which number to use, when to round, and how to convert without second-guessing.
US Cup To mL: Exact And Practical Values
The exact figure, 236.588 mL, comes from how US liquid volume is built: 1 US gallon is exactly 231 cubic inches, and a cup is 1⁄16 of that gallon. Since 1 cubic inch is 16.387064 mL, multiplying those constants gives 236.5882365 mL for one cup (exact to the conversion factors). Those constants are set in federal references and NIST tables.
Food labels play by a simpler rule. For nutrition facts, US regulations use a rounded serving-measure called the “legal cup”: 240 mL. If you’re matching package directions, use 240. If you’re following a US recipe or calibrating brewing gear, stick with 236.588.
When To Use 236.588 mL Versus 240 mL
- Home recipes and barista gear: 236.588 mL matches traditional US cookbooks, coffee ratios, and lab-style conversions.
- Nutrition labels and serving sizes: 240 mL is the legal serving cup printed on packages and nutrition panels.
Quick Chart: Cups To Milliliters (US Measuring Cup)
This chart uses the precise 236.588 mL value so your small fractions land where they should.
| US Cups | Milliliters (mL) | US Fluid Ounces |
|---|---|---|
| 1/8 cup | 29.573 mL | 1 fl oz |
| 1/4 cup | 59.147 mL | 2 fl oz |
| 1/3 cup | 78.863 mL | 2.67 fl oz |
| 1/2 cup | 118.294 mL | 4 fl oz |
| 2/3 cup | 157.726 mL | 5.33 fl oz |
| 3/4 cup | 177.441 mL | 6 fl oz |
| 1 cup | 236.588 mL | 8 fl oz |
| 1 1/4 cups | 295.735 mL | 10 fl oz |
| 1 1/2 cups | 354.882 mL | 12 fl oz |
| 2 cups | 473.176 mL | 16 fl oz (1 pt) |
Why The Numbers Differ By Context
In the kitchen you’ll see three “cup” standards used around the world. US recipes stick to the customary cup. Packaged foods in the US round to the 240 mL legal cup. Many countries measure with a 250 mL metric cup. If you cook across books, blogs, and brands, pick the standard that matches the source and convert from there.
The US Building Blocks Behind 236.588 mL
The route from a US cup to mL goes through two fixed rungs:
- US gallon: 1 gal = 231 in³ (fixed in federal packaging rules and standard tables).
- Cubic inch to milliliter: 1 in³ = 16.387064 mL (from SI-exact definitions).
Divide the gallon by 16 to get a cup, then convert cubic inches to mL with the exact factor. The result is 236.588 mL. These relationships are documented in NIST’s general tables and in the Code of Federal Regulations.
Where 240 mL Comes From
For labels, the US uses a rounded household measure so serving sizes don’t look like 236.588 mL on the box. The regulation sets teaspoon = 5 mL, tablespoon = 15 mL, fluid ounce = 30 mL, and cup = 240 mL for nutrition facts. You’ll see that language in the federal rule itself. 21 CFR 101.9.
Handy Equivalents You Can Trust
Once you know which “cup” you’re matching, the rest is easy math. These are the fixed rungs most cooks use day to day:
- 1 cup (US measuring cup): 8 US fluid ounces = 16 tablespoons = 48 teaspoons = 236.588 mL.
- Label shorthand: 1 cup (legal) = 240 mL; 1 tablespoon = 15 mL; 1 teaspoon = 5 mL. FDA nutrition labeling rule.
Picking The Right Number While You Cook
Use 236.588 mL when you’re translating a US cookbook, scaling a dough formula, or dialing in coffee ratios. Use 240 mL when you’re following directions straight off a nutrition label or a package that frames serving sizes in metric cups. For a metric-region recipe (Australia, New Zealand, much of Canada), assume 250 mL unless the author calls out US measures.
Milliliters In Other Cup Systems
Here’s a compact map of cup standards you’ll see in recipes and on labels:
| Cup Standard | Exact mL | Where You’ll See It |
|---|---|---|
| US customary cup | 236.588 mL | US cookbooks, brewing guides, lab-style conversions |
| US legal cup | 240 mL | US Nutrition Facts panels, serving sizes |
| Metric cup | 250 mL | Australia/NZ standards and many metric-region recipes |
| Imperial cup (historic) | ≈284 mL | Older UK/Canada references |
Worked Conversions You Can Copy
Converting Cups To mL (US Measuring Cup)
Multiply cups by 236.588. Round based on how precise the task is.
- 0.25 cup → 59.147 mL (round to 59 or 60 for everyday cooking)
- 0.5 cup → 118.294 mL (round to 118 or 120)
- 1.5 cups → 354.882 mL (round to 355 or 360)
- 2 cups → 473.176 mL (round to 473 or 475)
Converting mL To Cups (US Measuring Cup)
Divide mL by 236.588. A few common kitchen numbers:
- 100 mL → 0.423 cup (just under 1/2 cup)
- 150 mL → 0.634 cup (a bit over 5/8 cup)
- 250 mL → 1.057 cups (about 1 cup + 1 tablespoon)
- 500 mL → 2.114 cups (about 2 cups + 2 tablespoons)
Teaspoons, Tablespoons, Ounces: The Ladder In mL
If you convert through spoons or ounces, the arithmetic stays tidy using the same grounded constants:
- 1 teaspoon: 5 mL
- 1 tablespoon: 15 mL
- 1 US fluid ounce: 29.573 mL
- 8 US fluid ounces (1 cup): 236.588 mL
Those teaspoon and tablespoon numbers come straight from the labeling rule; the fluid-ounce constant follows from the same legal and NIST tables that fix cubic-inch and gallon relationships. 21 CFR 101.9 and NIST’s unit tables document the rest.
Metric-Region Recipes And US Gear
When a book from Australia or New Zealand calls for 1 cup of milk, that means 250 mL. If you pour with US measuring cups, you’ll be a little short. The simplest fix is to weigh ingredients by grams where the recipe lists them, or to reach for a metric jug and hit the 250 mL line. Standards Australia’s metric household spec and countless regional cookbooks treat 250 mL as the cup.
Practical Rounding That Won’t Spoil A Dish
For soups, stews, sauces, and most drinks, rounding to the nearest whole mL or even 5 mL is fine. For bread, espresso, and delicate pastry, keep the precise figure or weigh by grams. Precision matters more as hydration percentages and leavening get tight.
Troubleshooting: Why My Cup-To-mL Math Feels Off
Different Cup Printed On The Package
Package directions written for US shoppers often assume 240 mL. If your recipe card assumes the traditional US cup, the two won’t match perfectly. Pick one track and stick with it for that dish.
Measuring Dry Ingredients By Volume
Flour, cocoa, and powdered sugar compress. Two cooks can scoop two different weights into the same cup. When a recipe posts gram weights, prefer those. Use volume primarily for liquids and small add-ins, or level dry ingredients with a straight edge for consistency.
Thermal Expansion And Kitchen Reality
Lab constants assume temperatures like 20 °C for volume declarations. In a home kitchen, hot syrups and chilled juices shift volume slightly. The error is small for everyday cooking, but it’s a reason to use a scale for pastry syrups or confectionery work.
Authoritative References If You Want To Double-Check
For the legal cup and rounded spoon values used on US labels, read the FDA rule at 21 CFR 101.9. For the fixed US gallon, cubic-inch tables, and exact conversion factors that lead to 236.588 mL, NIST’s Handbook 44 Appendix C and conversion tables are the go-to references.
Bottom Line For Busy Cooks
If your source is a US recipe, treat 1 cup as 236.588 mL. If your source is a US Nutrition Facts panel or a package serving guide, treat it as 240 mL. If your source is from a metric-region cookbook, assume 250 mL unless the author warns you it’s using US measures. With those three cases in mind, you’ll hit the right volumes every time.