Appendix E — Metric / Imperial Conversions

The book uses metric AND imperial throughout. This appendix is your bidirectional reference. Keep it open while you cook in either system, or while you adapt a recipe written in the other.

A note on precision: cooking is forgiving. Round generously. The weights and volumes here are practical-cooking accurate. For pharmacology, please use a different book.

1. Temperature

The most common conversion in the kitchen. The relationship is °F = °C × 9/5 + 32 and °C = (°F − 32) × 5/9. Most thermometers display both. Memorize a few anchors and you'll never need a calculator.

Quick conversion shortcuts

• °C × 2 + 30 ≈ °F (close, off by a few degrees in baking range — fine for ovens, not for sous vide)
• (°F − 30) ÷ 2 ≈ °C (the reverse)
• A 25°F oven step is roughly a 14°C step.

2. Volume

Recipes from different traditions use different volume systems. The most important relationships:

A warning about cups

The "cup" varies by country: US legal cup is 240 mL, US customary is 236.6 mL, the metric cup (Australia, Canadian) is 250 mL, the UK Imperial cup is 284 mL. Books from each region use their own. When precision matters (baking), weigh ingredients instead.

Liquid measure conversions for common bottles

• 750 mL bottle (wine) ≈ 25 fl oz ≈ 3 cups + 2 Tbsp
• 1 L bottle ≈ 33.8 fl oz ≈ 4 cups + 1 Tbsp
• 1 gallon (US) = 3.785 L; 1 gallon (UK Imperial) = 4.546 L (these are different gallons!)

3. Weight

Weighing is more accurate than measuring by volume — especially for flour and other compressible ingredients.

Quick rule: 1 oz ≈ 28 g; 4 oz ≈ 113 g (a quarter pound); 1 lb ≈ 450 g; 1 kg ≈ 2.2 lb.

4. Volume → Weight (for common ingredients)

This is where weighing pays off — different ingredients pack differently. The same "cup" of flour can be 120 g (sifted) or 150 g (scooped and packed).

Flours and starches (per 1 cup / 240 mL — metric values are typical, vary by brand)

Sugars and salts

A note on salt: different salts have different crystal sizes, so the same volume gives different mass. By weight, salt is salt. This is why salting "by weight" is more reliable. If a recipe calls for "1 tsp salt" and is silent on which, it's likely table salt; substitute by weight rather than volume.

Dairy and fats

Common per-piece weights (rough)

5. Length

For pan sizes, dough thicknesses, knife work.

Common pan sizes

6. Pressure

For pressure cookers and atmospheric science.

At sea level, water boils at 100°C/212°F. At 2,000 m / 6,500 ft elevation it boils at ~93°C/200°F (roughly −1°C per 300 m, or −2°F per 1,000 ft of elevation). This matters in Denver, Mexico City, La Paz, Tibet, the Andes generally.

7. Energy and Power

For ovens and cooking power calculations.

A typical home gas burner is ~2 kW (~7,000 BTU/hr); a high-output wok burner can be 6 kW+ (20,000+ BTU/hr). An induction cooktop is ~2.4 kW per zone, but more efficiently delivered to the pan.

8. Baker's Percentages

Used in bread recipes (especially commercial / professional). The flour weight is set to 100%, and every other ingredient is expressed as a percentage of the flour weight.

A typical lean bread recipe:

Worked example. You have 500 g flour. Salt at 2% = 500 × 0.02 = 10 g. Water at 70% = 500 × 0.70 = 350 g. Yeast at 1% = 5 g.

This is how professional bakers scale — they think in percentages, not in cups.

9. The Honest Translation Notes

Cup-based recipes from different countries

If you're cooking from a 1950s American recipe, "1 cup" is 236.6 mL but rounding to 240 mL is fine. If you're cooking from an Australian recipe, "1 cup" is 250 mL — this matters in baking.

"1 stick of butter" (US)

= 1/2 cup = 8 Tbsp = 4 oz = 113 g.

Spoons across the Atlantic

US Tbsp = 14.8 mL (often called 15 mL); UK Tbsp = 15 mL; Australian Tbsp = 20 mL. Australian recipes have an unusually large tablespoon. This matters for baking. Most international cookbooks now use 15 mL.

Stick vs cube of butter

The US "stick" is unique. In Europe, butter sells in 250 g blocks. In the UK, 250 g packets. There is no "cube" of butter in modern usage.

10. Useful conversions you'll do constantly

• 1 oz = 28 g (round to 28; "30 g" is fine for cooking)
• 1 lb = 450 g (round; precise is 454)
• 1 cup = 240 mL (US legal)
• 1 Tbsp = 15 mL = 3 tsp
• 1 tsp = 5 mL
• 350°F = 175°C (the universal "moderate oven")
• 1 stick butter = 113 g
• 1 large egg ≈ 50 g (without shell)
• Water freezes 0°C / 32°F; boils 100°C / 212°F at sea level

11. The bigger principle

The metric system makes scaling and multiplication easy (everything is base-10). The imperial system has historical anchors (a teaspoon was an actual spoon used to measure medicine). Both work in the kitchen. Pick one, stick to it within a recipe, and consult this appendix when you switch.

When in doubt — especially in baking — weigh. A kitchen scale (digital, ~$15 / £12 / €13) is the single best investment for accuracy across both systems. Once you weigh, the metric vs. imperial debate ends, because grams are grams.

🔗 See also: Appendix A (Temperature & Time Charts) for detailed cooking temperatures by food; Appendix B (Glossary) for vocabulary; Appendix C (Kitchen Lab Master List) for experiment protocols using these conversions in practice.