This comprehensive reference contains all the essential conversion formulas for your unit conversion needs, organized by measurement category.
1. Length Conversions
Metric System (Base: Meter)
1 kilometer (km) = 1,000 meters
1 hectometer (hm) = 100 meters
1 decameter (dam) = 10 meters
1 meter (m) = 1 meter (base unit)
1 decimeter (dm) = 0.1 meters
1 centimeter (cm) = 0.01 meters
1 millimeter (mm) = 0.001 meters
1 micrometer (μm) = 0.000001 meters
1 nanometer (nm) = 0.000000001 meters
Imperial/US Customary to Metric
1 inch (in) = 2.54 cm = 0.0254 m
1 foot (ft) = 12 inches = 30.48 cm = 0.3048 m
1 yard (yd) = 3 feet = 36 inches = 0.9144 m
1 mile (mi) = 5,280 feet = 1,760 yards = 1.609344 km
1 nautical mile (nmi) = 1.852 km = 1,852 m
Conversion Formulas
Meters to Feet: feet = meters × 3.28084
Feet to Meters: meters = feet × 0.3048
Inches to Centimeters: cm = inches × 2.54
Centimeters to Inches: inches = cm ÷ 2.54
Kilometers to Miles: miles = km × 0.621371
Miles to Kilometers: km = miles × 1.609344
2. Weight/Mass Conversions
Metric System (Base: Kilogram)
1 metric ton (t) = 1,000 kilograms
1 kilogram (kg) = 1,000 grams
1 hectogram (hg) = 100 grams
1 decagram (dag) = 10 grams
1 gram (g) = 1 gram (base unit)
1 decigram (dg) = 0.1 grams
1 centigram (cg) = 0.01 grams
1 milligram (mg) = 0.001 grams
Imperial/US Customary to Metric
1 ounce (oz) = 28.3495 grams
1 pound (lb) = 16 ounces = 453.592 grams = 0.453592 kg
1 stone (st) = 14 pounds = 6.35029 kg
1 US ton = 2,000 pounds = 907.185 kg
1 UK ton (long ton) = 2,240 pounds = 1,016.047 kg
Conversion Formulas
Kilograms to Pounds: pounds = kg × 2.20462
Pounds to Kilograms: kg = pounds ÷ 2.20462
Grams to Ounces: ounces = grams × 0.035274
Ounces to Grams: grams = ounces × 28.3495
3. Temperature Conversions
Primary Temperature Scales
- Celsius (°C): Water freezes at 0°C, boils at 100°C
- Fahrenheit (°F): Water freezes at 32°F, boils at 212°F
- Kelvin (K): Absolute zero at 0K, water freezes at 273.15K
Conversion Formulas
Celsius to Fahrenheit: °F = °C × (9/5) + 32
Fahrenheit to Celsius: °C = (°F - 32) × (5/9)
Celsius to Kelvin: K = °C + 273.15
Kelvin to Celsius: °C = K - 273.15
Fahrenheit to Kelvin: K = (°F - 32) × (5/9) + 273.15
Kelvin to Fahrenheit: °F = (K - 273.15) × (9/5) + 32
Additional Temperature Scales
Celsius to Rankine: °R = (°C × 9/5) + 491.67
Celsius to Réaumur: °Ré = °C × 4/5
Fahrenheit to Rankine: °R = °F + 459.67
4. Volume Conversions
Metric System (Base: Liter)
1 kiloliter (kL) = 1,000 liters = 1 cubic meter
1 hectoliter (hL) = 100 liters
1 decaliter (daL) = 10 liters
1 liter (L) = 1 liter (base unit)
1 deciliter (dL) = 0.1 liters
1 centiliter (cL) = 0.01 liters
1 milliliter (mL) = 0.001 liters = 1 cubic centimeter
Imperial/US Customary to Metric
1 US fluid ounce (fl oz) = 29.5735 mL
1 US cup = 8 fl oz = 236.588 mL
1 US pint = 2 cups = 473.176 mL
1 US quart = 2 pints = 946.353 mL
1 US gallon = 4 quarts = 3.78541 L
1 UK gallon (Imperial) = 4.54609 L
1 UK pint = 568.261 mL
Conversion Formulas
Liters to US Gallons: gallons = liters × 0.264172
US Gallons to Liters: liters = gallons × 3.78541
Liters to UK Gallons: gallons = liters × 0.219969
Milliliters to Fluid Ounces: fl oz = mL × 0.033814
Fluid Ounces to Milliliters: mL = fl oz × 29.5735
5. Area Conversions
Metric System (Base: Square Meter)
1 square kilometer (km²) = 1,000,000 square meters
1 hectare (ha) = 10,000 square meters
1 are (a) = 100 square meters
1 square meter (m²) = 1 square meter (base unit)
1 square centimeter (cm²) = 0.0001 square meters
1 square millimeter (mm²) = 0.000001 square meters
Imperial/US Customary to Metric
1 square inch (in²) = 6.4516 cm²
1 square foot (ft²) = 144 in² = 929.030 cm² = 0.092903 m²
1 square yard (yd²) = 9 ft² = 0.836127 m²
1 acre = 4,840 yd² = 4,046.86 m² = 0.404686 hectares
1 square mile (mi²) = 640 acres = 2.58999 km²
Conversion Formulas
Square Meters to Square Feet: ft² = m² × 10.7639
Square Feet to Square Meters: m² = ft² × 0.092903
Hectares to Acres: acres = hectares × 2.47105
Acres to Hectares: hectares = acres × 0.404686
6. Speed/Velocity Conversions
Common Speed Units
1 meter per second (m/s) = base unit
1 kilometer per hour (km/h) = 0.277778 m/s
1 mile per hour (mph) = 0.44704 m/s
1 knot (kn) = 0.514444 m/s
1 foot per second (ft/s) = 0.3048 m/s
Conversion Formulas
m/s to km/h: km/h = m/s × 3.6
km/h to m/s: m/s = km/h ÷ 3.6
mph to km/h: km/h = mph × 1.60934
km/h to mph: mph = km/h × 0.621371
mph to m/s: m/s = mph × 0.44704
knots to mph: mph = knots × 1.15078
knots to km/h: km/h = knots × 1.852
7. Time Conversions
Standard Time Units
1 millennium = 1,000 years
1 century = 100 years
1 decade = 10 years
1 year = 365.25 days (average, accounting for leap years)
1 month = 30.44 days (average)
1 week = 7 days
1 day = 24 hours
1 hour = 60 minutes = 3,600 seconds
1 minute = 60 seconds
1 second = base unit
Conversion Formulas
Years to Days: days = years × 365.25
Days to Hours: hours = days × 24
Hours to Minutes: minutes = hours × 60
Minutes to Seconds: seconds = minutes × 60
Seconds to Milliseconds: milliseconds = seconds × 1,000
8. Pressure Conversions
Common Pressure Units
1 pascal (Pa) = 1 N/m² (base SI unit)
1 kilopascal (kPa) = 1,000 Pa
1 bar = 100,000 Pa = 100 kPa
1 atmosphere (atm) = 101,325 Pa = 1.01325 bar
1 torr = 133.322 Pa
1 mmHg = 1 torr = 133.322 Pa
1 psi (pounds per square inch) = 6,894.76 Pa
Conversion Formulas
Pa to psi: psi = Pa × 0.000145038
psi to Pa: Pa = psi × 6,894.76
bar to atm: atm = bar × 0.986923
atm to bar: bar = atm × 1.01325
mmHg to Pa: Pa = mmHg × 133.322
9. Energy Conversions
Common Energy Units
1 joule (J) = base SI unit
1 kilojoule (kJ) = 1,000 J
1 calorie (cal) = 4.184 J
1 kilocalorie (kcal) = 4,184 J
1 British thermal unit (BTU) = 1,055.06 J
1 kilowatt-hour (kWh) = 3,600,000 J
1 electronvolt (eV) = 1.602176 × 10⁻¹⁹ J
Conversion Formulas
J to cal: cal = J × 0.239006
cal to J: J = cal × 4.184
kWh to J: J = kWh × 3,600,000
BTU to J: J = BTU × 1,055.06
10. Power Conversions
Common Power Units
1 watt (W) = 1 J/s (base SI unit)
1 kilowatt (kW) = 1,000 W
1 megawatt (MW) = 1,000,000 W
1 horsepower (hp) = 745.7 W
1 BTU/hour = 0.293071 W
Conversion Formulas
W to hp: hp = W × 0.00134102
hp to W: W = hp × 745.7
kW to hp: hp = kW × 1.34102
Implementation Notes
Precision Guidelines
- For everyday conversions: 4-6 decimal places
- For scientific applications: 8-12 decimal places
- For display: Round to appropriate significant figures
Common Conversion Factors
π (pi) = 3.14159265359
Avogadro's number = 6.02214076 × 10²³
Speed of light = 299,792,458 m/s
Gravitational acceleration = 9.80665 m/s²
JavaScript Implementation Example
// Temperature conversions
function celsiusToFahrenheit(celsius) {
return (celsius * 9/5) + 32;
}
function fahrenheitToCelsius(fahrenheit) {
return (fahrenheit - 32) * 5/9;
}
// Length conversions
function metersToFeet(meters) {
return meters * 3.28084;
}
function feetToMeters(feet) {
return feet * 0.3048;
}
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