Metric ↔ Imperial Converter

Introduction

Cooking and baking across different measurement systems is a daily challenge in kitchens worldwide. The Metric ↔ Imperial Converter handles conversions across four measurement categories — weight, volume, length, and temperature — making it an essential tool for anyone working with recipes from different countries.

The metric system (grams, milliliters, centimeters, Celsius) is used in nearly every country except the United States, which primarily uses imperial units (ounces, cups, inches, Fahrenheit). This divide creates constant friction for home cooks following international recipes. A British baking recipe calls for 200g of flour, while its American equivalent uses 1.5 cups. A French cookbook lists oven temperature at 180°C, while an American oven displays 350°F.

This converter handles the four most common measurement categories with precise conversion factors based on international standards [nist-conversion]. Weight conversions use the international avoirdupois system, volume conversions use US customary units (note: US cups and imperial cups are different), length conversions use standard metric-English equivalents, and temperature conversions use the exact mathematical formula between Celsius and Fahrenheit.

How to Use

Select the measurement category — Weight, Volume, Length, or Temperature — using the radio buttons. Enter the value you want to convert, then select the source unit (From) and target unit (To). The result appears instantly.

The Formula

Each measurement category uses a specific conversion formula based on internationally agreed standards [bipm-si].

Reference Tables

Practical Tips

Use a digital kitchen scale for weight conversions. While this converter handles the math, for actual cooking, a scale that switches between grams and ounces is more practical. This converter is best for converting written recipes before you start cooking.

Be aware of cup size differences. US cups (236.6 mL) and imperial/UK cups (284 mL) are different. Most online recipes from the UK actually use metric weights (grams), which eliminates the ambiguity. Australian cups are 250 mL. If a recipe says "cup" without specifying, it is typically US.

Memorize key temperature benchmarks. 350°F = 180°C (most common baking temperature), 400°F = 200°C (roasting), and 425°F = 220°C (high-heat roasting). Knowing these three conversions covers 90% of oven cooking.

For baking, use weight not volume. A cup of flour can weigh anywhere from 110g to 150g depending on how it is scooped. Professional bakers always use weight measurements. Use the reference table to convert cup-based recipes to grams for more consistent results.

When NOT to use this converter: The converter does not handle non-linear conversions like cooking times, energy (calories to joules), or pressure (PSI to kPa). It also does not convert recipe-specific units like "a pinch" or "to taste."

Limitations

Volume-to-weight conversions for dry ingredients are inherently approximate because the density of ingredients varies by brand, grind, and packing method. A cup of King Arthur all-purpose flour weighs 120g, but a cup of Gold Medal flour weighs approximately 125g. The ingredient reference table provides average values.

The volume converter uses US customary units. Imperial (UK) volume units differ from US units for pints, quarts, and gallons (though fluid ounces are similar: US fl oz = 29.57 mL, UK fl oz = 28.41 mL). The imperial cup (284 mL) differs from the US cup (236.6 mL). For UK recipes, use weight measurements in grams rather than volume.

Temperature conversions assume the exact mathematical conversion. Oven temperatures listed in recipes are often rounded (e.g., 180°C is typically rounded to 350°F in the US, though the exact conversion is 356°F). The converter gives the mathematically precise value, which should be rounded to the nearest 10°F for practical oven use.

The length converter does not handle specialized units like nautical miles, chains, rods, or angstroms. It covers the common cooking, baking, and household measurement units.

Frequently Asked Questions

Why is 1 cup of flour not the same weight everywhere?

Flour compacts and settles during shipping and storage. Scooping flour directly from the bag packs it more densely than spooning it into the cup. The standard weight of 120g per cup is based on the 'spoon and level' method, but many home cooks use different techniques, resulting in 20-30g variations.

Is a US cup the same as a UK cup?

No. A US cup is 236.6 mL, while a UK (imperial) cup is 284 mL. This 20% difference can significantly affect recipes. When in doubt, use weight measurements in grams for the most accurate results across different measurement systems.

How do I convert British 'gas mark' oven temperatures?

Gas marks are used on UK ovens. Gas mark 1 = 275°F (140°C), gas mark 4 = 350°F (180°C), gas mark 7 = 425°F (220°C). Each gas mark increment equals approximately 25°F (14°C).

Why do some recipes use fluid ounces and others use weight ounces?

Fluid ounces (fl oz) measure volume, while ounces (oz) measure weight. One fluid ounce of water weighs approximately one ounce, but this 1:1 relationship does not hold for other ingredients like flour or oil. Use the weight category for ounces and the volume category for fluid ounces.

Can I convert square feet to square meters?

This converter handles linear length only. To convert area, remember that 1 square foot = 0.0929 square meters. For square inches to square centimeters, multiply by 6.4516.

Is 0°C the same as 0°F?

No. 0°C is the freezing point of water, equal to 32°F. 0°F is significantly colder, approximately -17.8°C. The two scales have different zero points and different degree sizes.

How many teaspoons are in a tablespoon?

In the US system, 1 tablespoon = 3 teaspoons. In the UK and Australia, 1 tablespoon = 4 teaspoons. The converter uses the US standard (3 tsp per tbsp). Australian tablespoons are also larger at 20 mL vs 15 mL for US/UK.

What is the difference between a pint in the US and UK?

A US pint is 473 mL (16 US fl oz). A UK pint is 568 mL (20 UK fl oz). British beer pints are larger, which is why ordering 'a pint' gives you more beer in London than in New York.

Can I convert between grams and cups for any ingredient?

The converter handles generic volume-to-volume and weight-to-weight conversions, not weight-to-volume. To convert 200g of flour to cups, you need to know the density of flour (approximately 120g per cup), which is specific to each ingredient.

How precise are the conversion factors?

The converter uses standard conversion factors defined by NIST (National Institute of Standards and Technology). The precision is sufficient for cooking and household use. For scientific applications requiring extreme precision, consult the official NIST or BIPM standards.

Does the converter handle metric prefixes like milli- and kilo-?

Yes. The converter includes common metric units: milliliters, liters, grams, kilograms, millimeters, centimeters, and meters. Less common units like deciliters (dL) or centigrams (cg) are not included.

What about converting between milliliters and drops or dashes?

Drops and dashes are informal measurements that vary by source. A typical drop is approximately 0.05 mL (about 1/20 mL). A dash is roughly 0.6 mL (1/8 teaspoon). These are too variable to include in a converter and should be treated as estimates.

References

1. [1]National Institute of Standards and Technology. "Guide to the SI: Metric Conversion Factors." NIST Special Publication 811.
2. [2]Bureau International des Poids et Mesures. "The International System of Units (SI), 9th Edition." 2019.
3. [3]USDA FoodData Central. "Weight, Volume, and Yield of Food Ingredients."
4. [4]King Arthur Baking Company. "Ingredient Weight Conversion Chart."
5. [5]McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. Scribner, 2004.
6. [6]López-Alt, J. Kenji. "Why Metric is Better for Baking." Serious Eats.