Quick Answer
1 US Cup = 237ml (8 fl oz)
1 Imperial Cup = 284ml (10 fl oz)
⚠️ Imperial cups are 20% larger — this difference can ruin your baking!
US Cups vs Imperial Cups: Understanding the Critical Difference
Ever followed a recipe to the letter and ended up with dry, crumbly cake or soggy cookies? Before you blame yourself, check if you're using the right "cup." The difference between US and Imperial (UK) cups is significant enough to turn a baking triumph into a disaster.
Key Measurements:
1 US Cup = 236.588 ml → 237ml
1 Imperial Cup = 284.131 ml → 284ml
Imperial cups are about 20% larger!
Quick Conversion Reference
| US Cups | Imperial Cups | Milliliters | Common Use |
|---|---|---|---|
| ¼ cup | 0.21 cups | 59 ml | Small liquid amounts |
| ⅓ cup | 0.28 cups | 79 ml | Oil in muffins |
| ½ cup | 0.42 cups | 118 ml | Milk in pancakes |
| 1 cup | 0.83 cups | 237 ml | Standard liquid measure |
| 2 cups | 1.66 cups | 473 ml | Cake batter liquids |
| 4 cups | 3.33 cups | 946 ml | Large batch recipes |
Why This Matters for Your Baking
That 20% difference isn't just a number on paper—it directly affects whether your cakes rise properly, your cookies spread correctly, and your bread has the right texture. Here's what happens when you use the wrong cup:
Using US Cups for UK Recipe:
- Too little liquid = dry, crumbly texture
- Bread won't rise properly
- Cakes may be dense and heavy
- Cookies might not spread correctly
Using Imperial Cups for US Recipe:
- Too much liquid = soggy, wet texture
- Batter may be too thin
- Longer baking times needed
- May overflow pan sizes
How the Cup Difference Affects Common Baking Ingredients
The 20% volume difference translates to significant weight differences for each ingredient. Here's exactly how much extra you're adding when using the wrong cup standard:
| Ingredient | 1 US Cup | 1 Imperial Cup | Difference |
|---|---|---|---|
| All-Purpose Flour | 120g (237ml) | 144g (284ml) | +24g (20%) |
| Granulated Sugar | 200g (237ml) | 240g (284ml) | +40g (20%) |
| Milk (liquid) | 237ml (244g) | 284ml (293g) | +47ml (20%) |
| Melted Butter | 227g (237ml) | 272g (284ml) | +45g (20%) |
| Brown Sugar (packed) | 220g (237ml) | 264g (284ml) | +44g (20%) |
| Vegetable Oil | 218g (237ml) | 262g (284ml) | +44g (20%) |
Real Example: Classic Vanilla Cake
US Recipe Calls For:
- 2 cups all-purpose flour (240g)
- 1½ cups sugar (300g)
- 1 cup milk (237ml)
- ½ cup melted butter (113g)
Using US Cups ✓
Perfect texture, proper rise, balanced sweetness
Using Imperial Cups ✗
- +48g flour = dry, dense cake
- +60g sugar = too sweet
- +47ml milk = batter overflow
- +23g butter = greasy texture
Pro Tip: Most Affected Ingredients
Flour is the most critical—that extra 24g per cup can make bread too dense and cakes too dry. Sugar comes second; 40g extra per cup affects both sweetness and texture (sugar holds moisture). For liquids like milk and oil, the 20% difference can make your batter too thin or cause it to overflow your pan size. Always use weight measurements (grams) for precision baking.
Related Measurement Conversions
Need more precision? These related converters will help you nail your measurements every time:
- Cups to Milliliters - Convert any cup measurement to precise ml for foolproof results
- Cups to Grams - The most accurate way to measure baking ingredients by weight
- Flour Cups to Grams - Essential for consistent bread and cake baking
- US to UK Tablespoons & Teaspoons - Spoon measurements differ too!
- Butter Cups to Grams - Perfect butter measurements for pastries
Other Measurement Differences to Watch
Cups aren't the only measurement that varies between the US and UK. Here's a complete comparison:
| Measurement | US | Imperial (UK) | Metric |
|---|---|---|---|
| Tablespoon | 14.79 ml | 17.76 ml | 15 ml |
| Teaspoon | 4.93 ml | 5.92 ml | 5 ml |
| Fluid Ounce | 29.57 ml | 28.41 ml | 30 ml (approx) |
| Pint | 473 ml (16 fl oz) | 568 ml (20 fl oz) | 500 ml |
Pro Tips for International Baking
- Check the recipe source: American blogs and websites use US cups, British sites use Imperial measurements
- Look for clues: If a recipe lists grams alongside cups, it's likely British or European
- When in doubt, use weight: Measuring by grams is universal and more accurate
- Invest in proper measuring tools: Buy both US and Imperial measuring cups, or use a kitchen scale
- Australian recipes: Watch out for metric cups (250ml) - yet another standard!
Common Recipe Conversions
For US Recipes in the UK:
Multiply US cup amounts by 0.83 to get Imperial cups
Or better yet: 1 US cup = 237ml, measure precisely with a liquid measuring cup
For UK Recipes in the US:
Multiply Imperial cup amounts by 1.2 to get US cups
Or: 1 Imperial cup = 284ml, use a liquid measuring cup marked in ml
📚 Historical Context: Why the Confusion?
The confusion stems from historical differences in measurement standardization:
- United States: Standardized the cup at 8 US fluid ounces (236.588 ml) in the 19th century
- British Empire: Used the imperial system with 1 cup = 10 imperial fluid ounces (284.131 ml)
- Canada: Officially uses metric but recipes often use US cups
- Australia/NZ: Use metric cups (250 ml) which are different from both!
Frequently Asked Questions
How many ml in a US cup?
A US cup equals exactly 236.588 ml, commonly rounded to 237ml for practical baking purposes. This is based on the US customary measurement of 8 fluid ounces.
How many ml in an Imperial (UK) cup?
An Imperial cup equals 284.131 ml, rounded to 284ml. This is based on 10 imperial fluid ounces. That's about 47ml more than a US cup!
Which countries use which cup system?
- US Cups (237ml): United States, Liberia, Myanmar
- Imperial Cups (284ml): United Kingdom (though metric is now standard)
- Metric Cups (250ml): Australia, New Zealand, Canada (sometimes)
- Metric only (ml/grams): Most of Europe, Asia, Africa, South America
Can I use US measuring cups for UK recipes?
You can, but you'll need to adjust the amounts. Since US cups are 20% smaller, you'll need to add more liquid to UK recipes. Better option: use a kitchen scale or measuring jug marked in ml for accuracy.
What about "coffee cups" in old recipes?
Old recipes might reference "coffee cups" or "teacups" which were actual drinking cups. These varied wildly but were generally:
- Coffee cup: 150-180ml (about ¾ US cup)
- Teacup: 120-150ml (about ½-⅔ US cup)
Should I always convert exactly?
For most recipes, close approximations work fine. But for delicate baked goods like macarons, choux pastry, angel food cake, or bread dough, precision matters more. When in doubt, measure by weight in grams for best results.
What happens if I use the wrong cup size?
Using US cups for UK recipes means 20% less liquid, resulting in dry, crumbly textures and dense cakes. Using Imperial cups for US recipes means 20% more liquid, causing soggy textures, thin batters, and longer baking times. Neither will give you the intended result!
Do I need different measuring cups for US and UK recipes?
The easiest solution is to invest in a kitchen scale and measure by weight (grams), which is universal and more accurate. Alternatively, buy measuring cups marked in ml and use our converter above, or purchase both US and Imperial measuring cup sets if you frequently use recipes from both regions.
🎉 Now you're equipped to tackle any recipe from anywhere in the world! Bookmark this page, and never let cup confusion ruin your baking again. Happy baking!