🛠️ Everyday UtilitiesLast updated May 3, 2026

Unit Conversion Guide 2026: Complete Metric & Imperial Converter — Length, Weight, Temperature, Volume, Speed & Digital Units

Master every conversion formula, chart, and technique from SI base units to cooking measurements and digital storage

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10+

Unit Categories

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300+

Conversions

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195 of 197

Countries Using Metric

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7 Units

SI Base Units

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15+

Tools Available

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May 2026

Updated

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Key Takeaways

Length anchors (exact per NIST): 1 inch = 2.54 cm, 1 foot = 30.48 cm, 1 yard = 91.44 cm, 1 mile = 1.60934 km, 1 metre = 3.28084 feet. Memorize these five and all other length conversions are derivable.
Weight anchors: 1 pound = 453.592 grams (exact by international agreement), 1 kg = 2.20462 lbs, 1 stone = 14 lbs = 6.350 kg, 1 metric ton = 1,000 kg = 2,204.62 lbs. Quick lbs → kg: divide by 2.2 (or divide by 2 and subtract 10%).
Temperature formulas: °F = (°C × 9/5) + 32; °C = (°F − 32) × 5/9; K = °C + 273.15. The only point where °F = °C is −40°. Body temperature: 37°C = 98.6°F. Water boils at 100°C = 212°F.
Volume critical distinction: 1 US gallon = 3.785 L vs. 1 UK imperial gallon = 4.546 L (20.1% larger). 1 US fluid oz = 29.574 mL; 1 UK fluid oz = 28.413 mL. Always specify US or UK in recipes and fuel economy comparisons.
Area and 3D volume: 1 sq ft = 0.0929 m², 1 acre = 4,047 m² = 43,560 sq ft, 1 hectare = 10,000 m² = 2.471 acres. Cubic: 1 cubic foot = 28.317 litres, 1 cubic metre = 264.17 US gallons.
Speed: 1 mph = 1.60934 km/h, 1 km/h = 0.62137 mph, 1 knot = 1.852 km/h = 1.151 mph. Rule of thumb: multiply mph × 1.6 for km/h. 60 mph = 96.56 km/h; US speed limit 65 mph = 104.6 km/h; EU limit 130 km/h = 80.8 mph.
Digital storage — two standards coexist: binary/IEC (1 KiB = 1,024 bytes; used by operating systems) vs. decimal/SI (1 KB = 1,000 bytes; used by hard drive manufacturers). A labelled “1 TB” drive shows as ~931 GiB in Windows/macOS due to this discrepancy.
Cooking: volume ≈ weight only for water. 1 cup flour = 120–130 g (varies by scooping); 1 cup sugar = 200 g; 1 cup butter = 227 g. For precise baking, always weigh in grams rather than measuring by volume.
Pressure and energy: 1 psi = 6.895 kPa, 1 bar = 100 kPa = 14.504 psi, standard atmosphere = 101.325 kPa. Energy: 1 kWh = 3,600,000 J, 1 food Calorie (kcal) = 4.184 kJ, 1 BTU = 1.055 kJ.
SI has exactly 7 base units (redefined 2019): second, metre, kilogram, ampere, kelvin, mole, candela. All derived units (newton, pascal, watt, volt, etc.) are combinations of these seven with exact relationships.

Unit conversion underpins every field of human activity — cooking European recipes, buying property measured in square metres, comparing fuel economy across continents, reading scientific papers in SI, or sizing cloud storage for enterprise IT. The US, Liberia, and Myanmar remain the only countries not officially metricated, making conversion fluency essential in our interconnected world. This guide — grounded in NIST SI unit definitions, BIPM standards, and IEC 80000-13 digital unit standards — covers every common conversion with exact formulas, worked examples, printable reference charts, and 15+ free converters. Use our universal unit converter for instant calculations.

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The SI Metric System: 7 Base Units, Prefixes & Why 195 Countries Use It

The International System of Units (SI), maintained by the BIPM and defined in the US by NIST, has exactly 7 base units: (1) metre (length), (2) kilogram (mass), (3) second (time), (4) ampere (electric current), (5) kelvin (temperature), (6) mole (amount of substance), (7) candela (luminous intensity). In 2019, all 7 were redefined using fixed numerical values of fundamental physical constants (Planck constant, elementary charge, Boltzmann constant, etc.) for maximum stability. SI prefixes apply to any unit: yocto (10⁻²⁴), zepto (10⁻²¹), atto (10⁻¹⁸), femto (10⁻¹⁵), pico (10⁻¹²), nano (10⁻⁹), micro (10⁻⁶), milli (10⁻³), centi (10⁻²), deci (10⁻¹), kilo (10³), mega (10⁶), giga (10⁹), tera (10¹²), peta (10¹⁵), exa (10¹⁸). Only three countries lack full metrication: the US, Liberia, and Myanmar — though the US uses SI exclusively in science, medicine, military, and international trade.

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Length & Distance Conversions: Inches, Feet, Metres, Miles & Kilometres

Exact anchor (per NIST): 1 inch = 2.54 cm. All other conversions derive from this. Imperial system: 12 inches = 1 foot; 3 feet = 1 yard; 1,760 yards = 1 mile = 5,280 feet. Metric conversion table: 1 inch = 2.54 cm; 1 foot = 30.48 cm = 0.3048 m; 1 yard = 91.44 cm = 0.9144 m; 1 mile = 1,609.34 m = 1.60934 km; 1 metre = 39.3701 inches = 3.28084 feet; 1 km = 0.62137 miles. Height conversion quick chart: 5′0″ = 152.4 cm; 5′5″ = 165.1 cm; 5′10″ = 177.8 cm; 6′0″ = 182.9 cm; 6′5″ = 195.6 cm. Running distances: 5 km = 3.107 miles; 10 km = 6.214 miles; half marathon = 21.098 km = 13.109 miles; full marathon = 42.195 km = 26.219 miles. Nautical: 1 nautical mile = 1,852 m = 1.1508 statute miles (used in aviation and maritime). Use our length converter for all distance calculations.

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Weight & Mass Conversions: Pounds, Kilograms, Stones, Ounces & Metric Tons

Key relationships: 1 pound (lb) = 453.59237 grams (exact); 1 kg = 2.20462 lbs; 1 oz (avoirdupois) = 28.3495 g; 1 stone (UK) = 14 lbs = 6.350 kg; 1 short ton (US) = 2,000 lbs = 907.2 kg; 1 metric ton (tonne) = 1,000 kg = 2,204.62 lbs; 1 long ton (UK) = 2,240 lbs = 1,016 kg. Troy weight (precious metals): 1 troy oz = 31.1035 g (heavier than avoirdupois oz = 28.35 g); 1 troy pound = 12 troy oz = 373.24 g. Quick mental math: lbs → kg: divide by 2.2; kg → lbs: multiply by 2.2. Better approximation: lbs ÷ 2 then subtract 10% (180 lbs → 90 − 9 = 81 kg vs. actual 81.65 kg). Body weight chart: 100 lbs = 45.4 kg; 130 lbs = 59.0 kg; 150 lbs = 68.0 kg; 180 lbs = 81.6 kg; 200 lbs = 90.7 kg; 220 lbs = 99.8 kg; 250 lbs = 113.4 kg. Use our weight converter for precise calculations.

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Temperature Conversions: Celsius, Fahrenheit, Kelvin & Rankine

Formulas: °F = (°C × 9/5) + 32; °C = (°F − 32) × 5/9; K = °C + 273.15; Rankine = °F + 459.67. Key reference points: absolute zero = −273.15°C = −459.67°F = 0 K; dry ice = −78.5°C = −09.3°F; water freezes = 0°C = 32°F; body temperature = 37°C = 98.6°F; room temperature = 20–22°C = 68–72°F; water boils (sea level) = 100°C = 212°F; bread bakes = 175°C = 347°F; steel melts = 1,370°C = 2,498°F. Oven conversion chart: 150°C = 302°F = Gas 2; 180°C = 356°F = Gas 4; 200°C = 392°F = Gas 6; 220°C = 428°F = Gas 7; 230°C = 446°F = Gas 8. Medical range: hypothermia < 35°C (95°F); normal 36.1–37.2°C (97–99°F); fever > 38°C (100.4°F). Unique property: −40° is identical in both Celsius and Fahrenheit scales. Use our temperature converter for instant results.

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Volume & Liquid Conversions: US/UK Gallons, Litres, Cups & Fluid Ounces

Critical US vs. UK split: 1 US gallon = 3.785 litres; 1 UK (imperial) gallon = 4.546 litres (20.1% larger). US volume chain: 1 US gallon = 4 quarts = 8 pints = 16 cups = 128 fl oz = 256 tablespoons = 768 teaspoons. Metric equivalents (US): 1 US fl oz = 29.574 mL; 1 US cup = 240 mL; 1 US pint = 473 mL; 1 US quart = 946 mL; 1 US gallon = 3,785 mL. UK equivalents: 1 UK fl oz = 28.413 mL; 1 UK pint = 568 mL; 1 UK quart = 1,137 mL; 1 UK gallon = 4,546 mL. Metric-to-US: 1 litre = 33.814 US fl oz = 4.227 US cups = 2.113 US pints = 0.264 US gallons. Fuel economy crosswalk: 30 mpg (US) = 7.84 L/100 km; 30 mpg (UK) = 9.41 L/100 km (UK mpg always sounds better than US mpg by ~20%). Use our volume converter.

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Area & 3D Volume Conversions: Square Feet, Acres, Hectares & Cubic Measures

Area conversions: 1 sq inch = 6.452 cm²; 1 sq foot = 929.03 cm² = 0.0929 m²; 1 sq yard = 0.836 m²; 1 sq mile = 2.590 km² = 640 acres; 1 acre = 43,560 sq ft = 4,047 m² = 0.405 hectares; 1 hectare = 10,000 m² = 2.471 acres = 107,639 sq ft. Property size reference: 500 sq ft = 46.5 m² (studio); 1,000 sq ft = 92.9 m²; 1,500 sq ft = 139 m²; 2,000 sq ft = 186 m²; 2,500 sq ft = 232 m²; 1 acre = 43,560 sq ft. 3D volume: 1 cubic inch = 16.387 mL; 1 cubic foot = 28.317 litres = 7.481 US gallons; 1 cubic yard = 764.6 litres; 1 cubic metre = 264.17 US gallons = 35.315 cubic feet. Concrete/construction: 1 cubic yard (CY) = 0.7646 m³ (standard US ready-mix unit). Use our area converter for all real estate and land calculations.

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Speed, Force & Pressure Conversions: mph, km/h, Knots, PSI & kPa

Speed: 1 mph = 1.60934 km/h = 0.44704 m/s = 0.86898 knots; 1 km/h = 0.62137 mph = 0.27778 m/s = 0.53996 knots; 1 knot = 1.852 km/h = 1.15078 mph; 1 m/s = 3.6 km/h = 2.237 mph. Speed reference: walking 3–5 km/h = 2–3 mph; cycling 20–30 km/h = 12–19 mph; car highway 100–130 km/h = 62–81 mph; commercial aircraft 900 km/h = 559 mph; sound (sea level, 20°C) = 343 m/s = 1,235 km/h. Force: 1 newton = 0.2248 lbf; 1 pound-force = 4.448 N. Pressure: 1 psi = 6.895 kPa = 0.06895 bar; 1 bar = 100 kPa = 14.504 psi; 1 atmosphere = 101.325 kPa = 14.696 psi; 1 mmHg = 133.3 Pa = 0.01934 psi. Tire pressure context: typical car tire 32–35 psi = 220–240 kPa. Use our speed converter.

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Digital Storage Conversions: KB vs. KiB, MB, GB, TB, PB & Network Speed

Binary/IEC standard (kibibyte, mebibyte, gibibyte — used by OS): 1 KiB = 2¹° = 1,024 bytes; 1 MiB = 2²° = 1,048,576 bytes; 1 GiB = 2³° = 1,073,741,824 bytes; 1 TiB = 2⁴° = 1,099,511,627,776 bytes; 1 PiB = 2⁵°. Decimal/SI standard (used by storage manufacturers): 1 KB = 10³ = 1,000 bytes; 1 MB = 10⁶ = 1,000,000 bytes; 1 GB = 10⁹; 1 TB = 10¹²; 1 PB = 10¹⁵. Gap consequence: a marketed “1 TB” SSD = 1,000,000,000,000 bytes = 931 GiB as shown by Windows/macOS — the ~7% gap is not missing data but a labelling convention difference. Network speeds use decimal bits: 1 Mbps = 1,000,000 bits/s; download “100 Mbps” = 12.5 MB/s (decimal) = 11.9 MiB/s (binary). Cloud storage reference: 1 full HD photo = ~4 MB; 1 minute 4K video = ~375 MB; 1 hour 4K = ~22.5 GB. Use our data size converter.

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Cooking & Baking Conversions: Cups, Tablespoons, Grams, Ounces & Millilitres

US volume hierarchy: 1 cup = 16 tablespoons = 48 teaspoons = 240 mL; 1 tablespoon (tbsp) = 3 teaspoons = 15 mL; 1 teaspoon (tsp) = 5 mL; ¼ cup = 4 tbsp = 60 mL; ½ cup = 8 tbsp = 120 mL; ¾ cup = 12 tbsp = 180 mL. Ingredient weight chart: all-purpose flour: 1 cup = 120–130 g; bread flour: 127 g; sugar (granulated): 200 g; sugar (powdered): 120 g; brown sugar (packed): 220 g; butter: 227 g (2 sticks); milk: 240 g; honey: 340 g; cocoa powder: 85 g; oats (rolled): 90 g; rice (dry): 185–200 g; breadcrumbs: 108 g. Liquid measures: 1 cup = 240 mL (US) vs. 250 mL (metric cup used in AU/CA). Ounce distinction: 1 fluid ounce = 29.57 mL (volume); 1 ounce = 28.35 g (weight). For professional baking accuracy, always weigh. Scaling recipes: for ×2 a recipe, simply double all weights; for volume, note that doubling a ¾ cup = 1½ cups (not always a single measuring cup size). Use our cooking converter.

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Dimensional Analysis: Convert Any Unit Step by Step (With Examples)

Dimensional analysis (the “factor-label” or “units-cancellation” method) is the systematic approach used in chemistry, physics, and engineering to convert any unit reliably. 3-step process: (1) write starting value with units; (2) multiply by conversion fractions (= 1) so unwanted units appear in the denominator (cancel); (3) compute. Example 1 — 60 mph to m/s: 60 miles/hr × (1,609.34 m / 1 mile) × (1 hr / 3,600 s) = 60 × 1,609.34 / 3,600 = 26.82 m/s. Example 2 — 25 kg/m³ to lbs/ft³: 25 kg/m³ × (2.20462 lb / 1 kg) × (1 m / 3.28084 ft)³ = 25 × 2.20462 / 35.3147 = 1.561 lbs/ft³. Example 3 — rate conversion: 90 km/h to m/s: 90 km/hr × (1,000 m / 1 km) × (1 hr / 3,600 s) = 90,000 / 3,600 = 25 m/s. This method catches errors automatically — if your units don’t cancel to the target unit, the setup is wrong. It extends to multi-step conversions with any number of intermediate units, compound units (km/h, kg/m³), or unit exponents (m², ft³).

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Divide cm by 2.54 to get total inches, then divide by 12 for feet (take floor), remainder is inches. Formula: feet = floor(cm / 30.48); inches = (cm − feet × 30.48) / 2.54. Example: 175 cm ÷ 2.54 = 68.9 inches → 5 feet 8.9 inches (5′8.9″). Height chart: 160 cm = 5′2.9″; 165 cm = 5′4.9″; 170 cm = 5′6.9″; 175 cm = 5′8.9″; 180 cm = 5′10.9″; 185 cm = 6′0.9″; 190 cm = 6′2.8″. Use our <a href="/category/tools/length-converter">length converter</a> for instant height conversion.

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

US gallon = 3.785 litres (128 US fluid ounces). UK imperial gallon = 4.546 litres (160 UK fluid ounces) — 20.1% larger. This matters critically for: fuel economy (UK car “40 mpg” ≈ 33 mpg US, or 7.1 L/100km); baking recipes (a UK pint = 568 mL vs. US pint = 473 mL); medicine dosing. Fluid ounces also differ: 1 US fl oz = 29.574 mL; 1 UK fl oz = 28.413 mL. When following international recipes, always identify which measuring system is used.

How do I convert miles to kilometres?

Multiply miles × 1.60934. Example: 10 miles = 16.093 km. Quick approximation: multiply by 1.6 (error < 0.6%). For km to miles: multiply by 0.62137. Key distances: marathon = 26.2 miles = 42.195 km; half marathon = 13.1 miles = 21.098 km. Speed limits: US 65 mph = 104.6 km/h; Germany autobahn 130 km/h = 80.8 mph. Running pace: 6:00/mile = 3:44/km; 7:00/mile = 4:22/km. Use our <a href="/category/tools/length-converter">length converter</a> for precise distance calculations.

How do I convert square feet to square metres?

1 sq ft = 0.09290 m². Multiply sq ft × 0.0929. Example: 1,500 sq ft × 0.0929 = 139.4 m². Reverse: multiply m² × 10.764 to get sq ft. Common property sizes: 400 sq ft = 37.2 m² (studio); 800 sq ft = 74.3 m²; 1,000 sq ft = 92.9 m²; 1,500 sq ft = 139.4 m²; 2,000 sq ft = 185.8 m²; 2,500 sq ft = 232.3 m². Land: 1 acre = 43,560 sq ft = 4,047 m²; 1 hectare = 10,000 m² = 2.471 acres. Use our <a href="/category/tools/area-converter">area converter</a> for real estate and land calculations.

What is the difference between KB, MB, GB, and TB?

Two standards coexist: Binary/IEC (used by operating systems): 1 KiB = 1,024 bytes; 1 MiB = 1,048,576 bytes; 1 GiB = 1,073,741,824 bytes; 1 TiB ≈ 1.1 trillion bytes. Decimal/SI (used by storage manufacturers): 1 KB = 1,000 bytes; 1 MB = 1,000,000 bytes; 1 GB = 1,000,000,000 bytes; 1 TB = 1,000,000,000,000 bytes. Result: a “1 TB” hard drive shows as ~931 GiB in Windows/macOS. For network speeds: 1 Mbps = 1,000,000 bits/second (decimal SI). Use our <a href="/category/logistics/data-size-converter">data size converter</a> for precise calculations.

How do I convert cups to grams for cooking and baking?

Volume → weight depends on ingredient density. Key conversions: all-purpose flour: 1 cup = 120–130 g (spoon & level) or up to 150 g (packed); bread flour: 1 cup = 127 g; granulated sugar: 1 cup = 200 g; brown sugar (packed): 1 cup = 220 g; powdered sugar: 1 cup = 120 g; butter: 1 cup = 227 g (2 US sticks); milk/water: 1 cup = 240 g; honey: 1 cup = 340 g; rolled oats: 1 cup = 90 g; rice (dry): 1 cup = 185–200 g. 1 tablespoon = 15 mL; 1 teaspoon = 5 mL. For precision baking, always weigh ingredients — volume measurements can vary ±30%.

How do I convert mph to km/h?

Multiply mph × 1.60934. Example: 60 mph × 1.609 = 96.56 km/h; 65 mph = 104.6 km/h; 75 mph = 120.7 km/h. For km/h to mph: multiply by 0.62137. Common conversions: 30 mph = 48.3 km/h (residential); 55 mph = 88.5 km/h; 100 km/h = 62.1 mph; 120 km/h = 74.6 mph; 130 km/h = 80.8 mph. Other speed units: 1 knot = 1.852 km/h = 1.151 mph (aviation & marine); 1 m/s = 3.6 km/h = 2.237 mph. Use our <a href="/category/tools/speed-converter">speed converter</a> for all unit conversions.

How do I convert litres to gallons?

For US gallons: divide litres by 3.785 (or multiply by 0.26417). Example: 50 litres ÷ 3.785 = 13.21 US gallons. For UK gallons: divide by 4.546 (or multiply by 0.21997). Practical contexts: car fuel tank (50 L = 13.2 US gal = 11.0 UK gal); petrol price comparison: £1.50/litre (UK) = £6.82/UK gallon; fuel economy: 30 mpg (US) = 7.84 L/100 km; 30 mpg (UK) = 9.41 L/100 km. For reverse: 1 US gallon = 3.785 L = 0.8327 UK gal. Use our <a href="/category/tools/volume-converter">volume converter</a> for precise liquid conversions.

What is dimensional analysis and how do I use it for unit conversion?

Dimensional analysis (the “factor-label” method) multiplies by conversion fractions equal to 1, chosen so unwanted units cancel. Steps: (1) write the starting value with units; (2) multiply by fractions (new unit / old unit) until original units cancel; (3) verify only target units remain; (4) calculate. Example — convert 60 mph to m/s: 60 miles/hour × (1,609.34 m / 1 mile) × (1 hour / 3,600 s) = (60 × 1,609.34) / 3,600 m/s = 96,560 / 3,600 = 26.82 m/s. The miles and hours cancel, leaving m/s. This technique works for any unit conversion across any number of steps.

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