Unit Conversion Quick Reference

Unit Conversion Reference

Converting between measurement systems is one of the most common everyday calculations. Memorizing a few key conversion factors and reference values makes estimation fast and accurate.

Length

1 inch = 2.54 cm (exact). 1 foot = 30.48 cm. 1 mile = 1.609 km. Quick mental math: multiply miles by 1.6 for km, divide km by 1.6 for miles. Or use the Fibonacci approximation: consecutive Fibonacci numbers approximate the mile/km ratio (5 miles ≈ 8 km, 8 miles ≈ 13 km).

Weight

1 pound = 453.6 grams. 1 kilogram = 2.205 pounds. 1 ounce = 28.35 grams. Quick mental math: double the kg and add 10% for pounds (70 kg ≈ 154 lbs: 140 + 14). For cooking, 1 stick of butter = 113g = 4 oz = 8 tablespoons.

Temperature

Fahrenheit to Celsius: (°F - 32) × 5/9. Celsius to Fahrenheit: (°C × 9/5) + 32. Key reference points: water freezes at 0°C/32°F, boils at 100°C/212°F. Room temperature is about 22°C/72°F. Body temperature is 37°C/98.6°F. For quick estimation: double Celsius, subtract 10%, add 32.

Volume

1 gallon (US) = 3.785 liters. 1 cup (US) = 236.6 mL. 1 tablespoon = 14.8 mL. 1 fluid ounce = 29.6 mL. Note: UK gallons and cups differ from US measurements. 1 UK gallon = 4.546 liters. Cooking volumes also differ between US, UK, Australian, and Japanese standards.

Area

1 square foot = 0.0929 m². 1 acre = 4,047 m² = 0.4047 hectares. 1 square mile = 2.59 km². For real estate: multiply square meters by 10.76 for square feet. A football field is about 1.32 acres or 0.53 hectares.