🛠️ Everyday UtilitiesLast updated March 14, 2026

Unit Conversion Guide: Length, Weight, Temperature & More

Convert anything to anything — the complete reference

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Key Takeaways

Length: 1 inch = 2.54 cm, 1 foot = 30.48 cm, 1 mile = 1.609 km, 1 metre = 3.281 feet.
Weight: 1 lb = 0.4536 kg, 1 kg = 2.2046 lbs, 1 stone = 14 lbs = 6.35 kg.
Temperature: °F = (°C × 9/5) + 32. °C = (°F − 32) × 5/9. Quick reference: 0°C = 32°F, 100°C = 212°F.
Volume: 1 gallon (US) = 3.785 litres, 1 litre = 0.2642 US gallons. UK gallon ≠ US gallon (4.546L vs 3.785L).
Digital: 1 KB = 1,024 bytes (binary) or 1,000 bytes (SI). Context determines which standard applies.

Unit conversion is one of the most universally needed calculations — whether you're cooking with a European recipe, buying lumber measured in different systems, converting currencies for international shopping, or working with data sizes in IT. The US, Liberia, and Myanmar are the only countries not officially on the metric system, making conversion skills essential for an interconnected world. This guide — referencing NIST SI unit definitions and the BIPM (International Bureau of Weights and Measures) — covers every common conversion with formulas, charts, and our free unit converter tool.

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Length & Distance Conversions

The metric system uses metres with prefixes (mm, cm, m, km), while the imperial system uses inches, feet, yards, and miles. Key relationships: 1 inch = 2.54 cm (exact, per NIST), 1 foot = 12 inches = 30.48 cm, 1 yard = 3 feet = 91.44 cm, 1 mile = 5,280 feet = 1.609 km, 1 km = 0.6214 miles. For height conversion: multiply feet by 30.48, add remaining inches × 2.54 for total cm. Example: 5'10" = (5 × 30.48) + (10 × 2.54) = 177.8 cm. Use our CM to Feet converter for instant results.

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Weight & Mass Conversions

Imperial uses ounces (oz) and pounds (lb); metric uses grams (g) and kilograms (kg). Key: 1 lb = 16 oz = 453.6 g, 1 kg = 2.205 lb, 1 oz = 28.35 g, 1 metric ton = 1,000 kg = 2,205 lbs. UK also uses stone (1 stone = 14 lbs). Quick mental math: to convert lbs to kg, divide by 2 and subtract 10% of that result. Example: 180 lbs → 90 − 9 = 81 kg (actual: 81.6 kg). The BIPM defines the kilogram via the Planck constant. Use our unit converter for precise weight conversions.

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Temperature Conversions

Three scales: Celsius (water freezes at 0°, boils at 100°), Fahrenheit (freezes at 32°, boils at 212°), and Kelvin (absolute zero = 0K = −273.15°C). °F = (°C × 9/5) + 32. °C = (°F − 32) × 5/9. K = °C + 273.15. Handy benchmarks: −40° is the same in both °F and °C. Body temperature: 98.6°F = 37°C. Room temperature: 68–72°F = 20–22°C. Oven temperatures: 350°F = 177°C, 400°F = 204°C, 450°F = 232°C. There are currently seven SI base units defined by NIST, with the kelvin being the base unit of thermodynamic temperature.

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Volume, Speed & Digital Conversions

Volume: 1 US gallon = 3.785 L, 1 UK gallon = 4.546 L, 1 cup = 240 mL, 1 fluid oz = 29.57 mL, 1 litre = 33.81 US fl oz. Speed: 1 mph = 1.609 km/h, 1 km/h = 0.6214 mph. Digital storage: 1 KB = 1,024 bytes (binary/IEC) or 1,000 bytes (SI/decimal), 1 MB = 1,024 KB, 1 GB = 1,024 MB, 1 TB = 1,024 GB. Network speed typically uses decimal (1 Mbps = 1,000,000 bits/sec) while storage uses binary. Use our data size converter for digital unit conversions or our universal unit converter for all measurement types.

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Related Tools & Calculators

3 free tools linked to this guide

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Unit Converter

Convert between 200+ units across length, weight, volume, temperature, and more.

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CM to Feet Converter

Convert centimetres to feet and inches with precision.

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Data Size Converter

Convert between bytes, KB, MB, GB, TB, and other digital storage units.

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Frequently Asked Questions

How do I convert Celsius to Fahrenheit?

°F = (°C × 9/5) + 32. For example, 25°C = (25 × 1.8) + 32 = 77°F. Quick trick: double the Celsius, subtract 10%, add 32. For Fahrenheit to Celsius: °C = (°F − 32) × 5/9.

How many kg in a pound?

1 pound = 0.45359 kg. To convert lbs to kg, multiply by 0.4536. To convert kg to lbs, multiply by 2.2046. Quick estimate: divide lbs by 2 and subtract 10% (e.g., 150 lbs ≈ 68 kg).

How do I convert cm to inches?

1 inch = 2.54 cm, so divide centimetres by 2.54 to get inches. For example, 170 cm = 66.93 inches = 5 feet 6.93 inches. To convert to feet and inches: divide total inches by 12 for feet, remainder is inches.

What is the difference between a US gallon and a UK gallon?

A US gallon = 3.785 litres (128 US fluid ounces). A UK (imperial) gallon = 4.546 litres (160 UK fluid ounces). The UK gallon is about 20% larger. Always check which gallon system a recipe or specification uses.

How do I convert between metric and imperial for cooking?

Key conversions: 1 cup = 240 mL, 1 tablespoon = 15 mL, 1 teaspoon = 5 mL, 1 ounce = 28.35 grams. For baking precision, weigh ingredients in grams rather than using volume measurements — 1 cup of flour can vary by 30% depending on how it's scooped.

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