Unit Conversion Quick Reference
Convert between metric and imperial units for length, weight, temperature, volume, and area with common reference values.
Percentage Calculator
Calculate percentages, increases, decreases, and ratios
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 โ 8 km, 8 miles โ 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 โ 154 lbs: 140 + 14). For cooking, 1 stick of butter = 113g = 4 oz = 8 tablespoons.
Temperature
Fahrenheit to Celsius: (ยฐF - 32) ร 5/9. Celsius to Fahrenheit: (ยฐC ร 9/5) + 32. Key reference points: water freezes at 0ยฐC/32ยฐF, boils at 100ยฐC/212ยฐF. Room temperature is about 22ยฐC/72ยฐF. Body temperature is 37ยฐC/98.6ยฐF. 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 mยฒ. 1 acre = 4,047 mยฒ = 0.4047 hectares. 1 square mile = 2.59 kmยฒ. For real estate: multiply square meters by 10.76 for square feet. A football field is about 1.32 acres or 0.53 hectares.
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