🧪 Volume Unit Converter — 14 Units
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Volume Conversion
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All 14 Units Simultaneously
⚠️ Disclaimer: All conversion factors are exact per NIST SP 811. US and UK (imperial) gallons are different units — always verify which gallon a source uses before calculating. For cooking, some international recipes use a metric cup of 250 mL rather than the US cup of 236.588 mL.
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Sources & Methodology
All conversion factors are exact per NIST SP 811 and the International System of Units (SI). The US gallon definition follows the US customary system (231 cubic inches). The UK imperial gallon follows the UK Weights and Measures Act 1985 (4.54609 litres exactly).
NIST SP 811 — Guide for the Use of the International System of Units
Authoritative US source for exact conversion factors. Key exact factors: 1 US gallon = 231 in³ exactly; 1 inch = 2.54 cm exactly; therefore 1 US gallon = 231 × (2.54)³ cm³ = 3,785.411784 mL = 3.785411784 L exactly. 1 US fl oz = 1/128 US gallon = 29.5735295625 mL exactly.
UK Weights and Measures Act 1985 — Imperial Gallon Definition
The UK imperial gallon is defined as exactly 4.54609 litres per the Weights and Measures Act 1985. This replaced the earlier definition based on water weight. The imperial fluid ounce = 1/160 imperial gallon = 28.4130625 mL exactly.
Exact Conversion Factors (NIST SP 811 & UK Weights and Measures Act 1985):
1 L = 1,000 mL (exact) • 1 m³ = 1,000 L (exact) 1 US gal = 3.785411784 L (exact) • 1 UK gal = 4.54609 L (exact) 1 US fl oz = 29.5735295625 mL (exact) • 1 UK fl oz = 28.4130625 mL (exact) 1 US cup = 236.5882365 mL (exact = 8 US fl oz) 1 US pint = 473.176473 mL (exact = 16 US fl oz) 1 UK pint = 568.26125 mL (exact = 20 UK fl oz) 1 US tbsp = 14.7867648 mL (exact = 0.5 US fl oz) 1 US tsp = 4.92892159 mL (exact = 1/6 US fl oz) Base unit: millilitre (mL). All units convert through mL for precision.
1 L = 1,000 mL (exact) • 1 m³ = 1,000 L (exact) 1 US gal = 3.785411784 L (exact) • 1 UK gal = 4.54609 L (exact) 1 US fl oz = 29.5735295625 mL (exact) • 1 UK fl oz = 28.4130625 mL (exact) 1 US cup = 236.5882365 mL (exact = 8 US fl oz) 1 US pint = 473.176473 mL (exact = 16 US fl oz) 1 UK pint = 568.26125 mL (exact = 20 UK fl oz) 1 US tbsp = 14.7867648 mL (exact = 0.5 US fl oz) 1 US tsp = 4.92892159 mL (exact = 1/6 US fl oz) Base unit: millilitre (mL). All units convert through mL for precision.
Last reviewed: April 2026
Volume Conversion Guide — US vs UK, Cooking Units & More
Volume conversion is one of the most practically important unit conversions in everyday life — from cooking recipes and beverage sizes to fuel economy and scientific measurements. The main complexity is that the US and UK use systems with the same names but different sizes, particularly for gallons, pints, and fluid ounces. This guide covers every major volume unit and its exact conversion factor.
The #1 Error: US Gallon vs UK Imperial Gallon
⚠️ Critical difference most converters don’t highlight:
US gallon = 3.785411784 litres (231 cubic inches, used in the United States)
UK imperial gallon = 4.54609 litres (used in the UK, Canada for some purposes)
The UK gallon is 20% larger than the US gallon. When comparing fuel economy between the US (mpg) and the UK (mpg), this difference is significant — a car achieving 40 UK mpg is equivalent to only about 33.3 US mpg. Always confirm which gallon a source is using.
US gallon = 3.785411784 litres (231 cubic inches, used in the United States)
UK imperial gallon = 4.54609 litres (used in the UK, Canada for some purposes)
The UK gallon is 20% larger than the US gallon. When comparing fuel economy between the US (mpg) and the UK (mpg), this difference is significant — a car achieving 40 UK mpg is equivalent to only about 33.3 US mpg. Always confirm which gallon a source is using.
Common Volume Conversions Reference Table
| From | To mL | To Litres | To US fl oz | To US cups |
|---|---|---|---|---|
| 1 US tsp | 4.929 | 0.004929 | 0.1667 | 0.02083 |
| 1 US tbsp | 14.787 | 0.014787 | 0.5 | 0.0625 |
| 1 US fl oz | 29.574 | 0.029574 | 1 | 0.125 |
| 1 US cup | 236.588 | 0.236588 | 8 | 1 |
| 1 US pint | 473.176 | 0.473176 | 16 | 2 |
| 1 US quart | 946.353 | 0.946353 | 32 | 4 |
| 1 US gallon | 3,785.41 | 3.78541 | 128 | 16 |
| 1 UK pint | 568.261 | 0.568261 | 19.215 | 2.402 |
| 1 UK gallon | 4,546.09 | 4.54609 | 153.72 | 19.215 |
| 1 Litre | 1,000 | 1 | 33.814 | 4.2268 |
Cooking Volume Units — US vs Metric
Cooking is the most common reason people need volume conversions. International recipe books frequently mix US cups with metric millilitres. Here are the exact definitions:
- 1 US teaspoon (tsp) = 4.92892 mL — for cooking, universally rounded to 5 mL
- 1 US tablespoon (tbsp) = 14.7868 mL = 3 teaspoons — rounded to 15 mL in metric cooking
- 1 US cup = 236.588 mL = 16 tablespoons = 8 fl oz
- UK/metric tablespoon = exactly 15 mL (slightly more than US tablespoon)
- Metric cup (Australia, Canada) = exactly 250 mL — different from US cup of 236.588 mL
🍳 Recipe tip: When converting a US recipe to metric, the difference between a US cup (236.6 mL) and a metric cup (250 mL) is about 5.7%. For most cooking this is negligible, but for precise baking (especially for bread or pastry), use the exact millilitre equivalent of the US cup amount rather than rounding to metric cups.
Real-World Volume Reference
| Volume | mL | fl oz (US) | Cups | Context |
|---|---|---|---|---|
| Shot (US) | 44.4 | 1.5 | 0.19 | Standard US cocktail shot |
| Can of beer/soda | 355 | 12 | 1.5 | Standard US/Canada can |
| 500 mL bottle | 500 | 16.91 | 2.11 | Common water bottle |
| Wine bottle | 750 | 25.36 | 3.17 | Standard 750 mL bottle |
| 1 litre bottle | 1,000 | 33.81 | 4.23 | Standard 1L water/soda |
| 2 litre bottle | 2,000 | 67.63 | 8.45 | Large soda bottle |
| US gallon jug | 3,785 | 128 | 16 | US milk gallon |
| Average bathtub | 189,000 | 6,393 | 799 | ~50 US gallons |
UK vs US Pint — Why a Pint of Beer Differs
A UK imperial pint = 568.261 mL (20 UK fl oz), while a US liquid pint = 473.176 mL (16 US fl oz). The UK pint is approximately 20% larger. This is why a “pint” of beer in a British pub contains significantly more than a “pint” in an American bar. When travelling, be aware that ordering a pint in the UK gives you ~568 mL, while in the US you receive ~473 mL.
Frequently Asked Questions
Exactly 3.785411784 litres per NIST. Quick mental math: roughly 3.785 L or “just under 4 litres.” To convert US gallons to litres, multiply by 3.785411784. Example: 5 US gallons × 3.785 = 18.927 litres.
Exactly 4.54609 litres per the UK Weights and Measures Act 1985. The UK gallon is 20% larger than the US gallon. 1 UK gallon = 4.54609 L vs 1 US gallon = 3.785 L. Always confirm which gallon a source is using, especially for fuel economy comparisons.
1 US fluid ounce = 29.5735295625 mL exactly. For quick mental math: 1 fl oz ≈ 30 mL (1.4% over). 1 UK imperial fluid ounce = 28.4130625 mL exactly. Most recipes refer to US fluid ounces.
1 US cup = 236.5882365 mL exactly (= 8 US fl oz). 1 metric/Australian cup = 250 mL exactly. US recipes use 236.588 mL cups. When converting US recipes to metric, use the exact 236.588 mL figure for baking accuracy.
Multiply US cups by 236.5882 to get mL. Example: 2.5 cups × 236.5882 = 591.47 mL. Reverse: divide mL by 236.5882 to get US cups. Example: 500 mL ÷ 236.5882 = 2.1134 cups.
Exactly 16 US tablespoons = 1 US cup. The chain: 1 cup = 8 fl oz = 16 tablespoons = 48 teaspoons. 1 US tablespoon = 14.7868 mL. 3 teaspoons = 1 tablespoon exactly.
1 US tablespoon = 14.7867648 mL exactly. 1 UK/metric tablespoon = 15 mL exactly. For cooking, the difference is negligible — most metric recipes define 1 tablespoon as 15 mL. To convert tablespoons to mL, multiply by 14.787 (US) or 15 (metric).
500 mL = 2.1134 US cups. Calculation: 500 ÷ 236.5882 = 2.1134 cups. Practically: 500 mL is 2 cups plus about 1 tablespoon. A 500 mL water bottle is just over 2 US cups (16.9 fl oz).
1 litre = 33.8140227 US fluid ounces. Quick references: 500 mL = 16.91 fl oz; 750 mL = 25.36 fl oz; 2 litres = 67.63 fl oz. For mental math: 1 litre ≈ 34 fl oz.
UK pint = 568.261 mL (20 UK fl oz). US pint = 473.176 mL (16 US fl oz). The UK pint is about 20% larger. This is why a pub pint in the UK contains more beer than a US bar pint.
1 litre = 4.22675 US cups. To convert litres to cups, multiply by 4.22675. Example: 1.5 litres × 4.22675 = 6.340 cups. For rough estimates: 1 litre is just over 4 cups.
US gallons to litres: multiply by 3.785411784. Example: 10 US gal × 3.785 = 37.854 L. UK gallons to litres: multiply by 4.54609. Example: 10 UK gal × 4.546 = 45.461 L. Reverse (litres to US gallons): multiply by 0.264172. Litres to UK gallons: multiply by 0.219969.
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