Unit Conversion Chart: The Complete Guide to Converting Any Measurement
Whether you are converting kilometers to miles for a road trip, grams to ounces for a recipe, or Celsius to Fahrenheit to understand the weather forecast — this unit conversion chart is the only reference you will ever need. Covering 40+ categories and over 750 units with instant, accurate calculations.
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What Is Unit Conversion?
Unit conversion is the process of changing a measurement from one unit to another without altering the quantity it represents. We use conversion factors — known equivalences such as 1 inch = 2.54 cm — to multiply or divide a value so it is expressed in a different unit. This technique, often called dimensional analysis, is fundamental in science, engineering, cooking, healthcare, and everyday life.
Why Unit Conversion Matters
- Global standardization — enables effective communication across different measurement systems used worldwide.
- Scientific accuracy — ensures precise, reproducible results in research, medicine, and engineering.
- Everyday practical use — from following a recipe in metric units to checking your luggage weight in pounds before a flight.
- Engineering & construction — architects and builders frequently convert between imperial and metric plans, especially on international projects.
Metric vs. Imperial Systems — A Quick Overview
The metric system (SI) is used by the vast majority of the world and is built on powers of ten, making conversions within the system straightforward. The imperial / US customary system is used primarily in the United States, Liberia, and Myanmar for everyday measurements. Converting between the two systems is where most people need a reliable unit conversion chart.
| Feature | Metric (SI) | Imperial / US Customary |
|---|---|---|
| Base length unit | Meter (m) | Foot (ft) / Inch (in) |
| Base mass unit | Kilogram (kg) | Pound (lb) |
| Temperature | Celsius (°C) | Fahrenheit (°F) |
| Scaling | Powers of 10 (kilo, centi, milli…) | Varied ratios (12 in/ft, 3 ft/yd, 5280 ft/mi) |
| Used by | ~95% of the world | United States, Liberia, Myanmar |
Complete Unit Conversion Charts
Reference tables for the most common measurement categories. All conversion factors are verified against international standards (NIST SP 811, BIPM SI).
Length & Distance Conversion Chart
Quick Reference
1 inch = 2.54 cm | 1 foot = 0.3048 m | 1 yard = 0.9144 m | 1 mile = 1.609 km | 1 meter = 3.281 ft
| Unit | mm | cm | m | km | in | ft | yd | mi |
|---|---|---|---|---|---|---|---|---|
| 1 Millimeter | 1 | 0.1 | 0.001 | 0.000001 | 0.03937 | 0.003281 | 0.001094 | 6.214×10⁻⁷ |
| 1 Centimeter | 10 | 1 | 0.01 | 0.00001 | 0.3937 | 0.03281 | 0.01094 | 6.214×10⁻⁶ |
| 1 Meter | 1,000 | 100 | 1 | 0.001 | 39.37 | 3.281 | 1.094 | 0.000621 |
| 1 Kilometer | 1,000,000 | 100,000 | 1,000 | 1 | 39,370 | 3,281 | 1,094 | 0.6214 |
| 1 Inch | 25.4 | 2.54 | 0.0254 | 0.0000254 | 1 | 0.08333 | 0.02778 | 0.00001578 |
| 1 Foot | 304.8 | 30.48 | 0.3048 | 0.000305 | 12 | 1 | 0.3333 | 0.000189 |
| 1 Yard | 914.4 | 91.44 | 0.9144 | 0.000914 | 36 | 3 | 1 | 0.000568 |
| 1 Mile | 1,609,344 | 160,934 | 1,609.3 | 1.609 | 63,360 | 5,280 | 1,760 | 1 |
Weight & Mass Conversion Chart
Quick Reference
1 lb = 453.6 g | 1 oz = 28.35 g | 1 kg = 2.205 lb | 1 stone = 6.35 kg | 1 metric ton = 1,000 kg
| Unit | mg | g | kg | oz | lb | st | t (metric) |
|---|---|---|---|---|---|---|---|
| 1 Milligram | 1 | 0.001 | 0.000001 | 3.527×10⁻⁵ | 2.205×10⁻⁶ | 1.575×10⁻⁷ | 1×10⁻⁹ |
| 1 Gram | 1,000 | 1 | 0.001 | 0.03527 | 0.002205 | 0.000157 | 0.000001 |
| 1 Kilogram | 1,000,000 | 1,000 | 1 | 35.27 | 2.205 | 0.1575 | 0.001 |
| 1 Ounce | 28,350 | 28.35 | 0.02835 | 1 | 0.0625 | 0.004464 | 2.835×10⁻⁵ |
| 1 Pound | 453,592 | 453.6 | 0.4536 | 16 | 1 | 0.07143 | 0.000454 |
| 1 Stone | 6,350,293 | 6,350 | 6.35 | 224 | 14 | 1 | 0.00635 |
| 1 Metric Ton | 1×10⁹ | 1,000,000 | 1,000 | 35,274 | 2,205 | 157.5 | 1 |
Volume & Capacity Conversion Chart
Quick Reference
1 US gallon = 3.785 L | 1 cup (US) = 236.6 mL | 1 fl oz = 29.57 mL | 1 liter = 0.2642 US gal
| Unit | mL | L | fl oz (US) | cup (US) | pt (US) | qt (US) | gal (US) |
|---|---|---|---|---|---|---|---|
| 1 Milliliter | 1 | 0.001 | 0.03381 | 0.004227 | 0.002114 | 0.001057 | 0.000264 |
| 1 Liter | 1,000 | 1 | 33.81 | 4.227 | 2.113 | 1.057 | 0.2642 |
| 1 Fluid Ounce | 29.57 | 0.02957 | 1 | 0.125 | 0.0625 | 0.03125 | 0.007813 |
| 1 Cup (US) | 236.6 | 0.2366 | 8 | 1 | 0.5 | 0.25 | 0.0625 |
| 1 Pint (US) | 473.2 | 0.4732 | 16 | 2 | 1 | 0.5 | 0.125 |
| 1 Quart (US) | 946.4 | 0.9464 | 32 | 4 | 2 | 1 | 0.25 |
| 1 Gallon (US) | 3,785 | 3.785 | 128 | 16 | 8 | 4 | 1 |
Temperature Conversion Chart
Conversion Formulas
| Description | °F | °C | K |
|---|---|---|---|
| Absolute zero | −459.67 | −273.15 | 0 |
| Freezing point of water | 32 | 0 | 273.15 |
| Room temperature | 68 | 20 | 293.15 |
| Human body temperature | 98.6 | 37 | 310.15 |
| Boiling point of water | 212 | 100 | 373.15 |
Area Conversion Chart
Quick Reference
1 acre = 43,560 ft² = 4,047 m² | 1 hectare = 10,000 m² = 2.471 acres | 1 mi² = 2.59 km² | 1 ft² = 0.0929 m²
| Unit | cm² | m² | in² | ft² | yd² | Acres | Hectares |
|---|---|---|---|---|---|---|---|
| 1 cm² | 1 | 0.0001 | 0.155 | 0.001076 | 0.00012 | 2.471×10⁻⁸ | 1×10⁻⁸ |
| 1 m² | 10,000 | 1 | 1,550 | 10.76 | 1.196 | 0.000247 | 0.0001 |
| 1 in² | 6.452 | 0.000645 | 1 | 0.006944 | 0.000772 | 1.594×10⁻⁷ | 6.452×10⁻⁸ |
| 1 ft² | 929 | 0.0929 | 144 | 1 | 0.1111 | 2.296×10⁻⁵ | 9.29×10⁻⁶ |
| 1 Acre | 4.047×10⁷ | 4,047 | 6,272,640 | 43,560 | 4,840 | 1 | 0.4047 |
| 1 Hectare | 1×10⁸ | 10,000 | 1.55×10⁷ | 107,639 | 11,960 | 2.471 | 1 |
Speed & Velocity Conversion Chart
Quick Reference
1 mph = 1.609 km/h | 1 m/s = 3.6 km/h | 1 knot = 1.852 km/h | 1 km/h = 0.6214 mph
| Unit | m/s | km/h | mph | ft/s | knots |
|---|---|---|---|---|---|
| 1 m/s | 1 | 3.6 | 2.237 | 3.281 | 1.944 |
| 1 km/h | 0.2778 | 1 | 0.6214 | 0.9113 | 0.5400 |
| 1 mph | 0.4470 | 1.609 | 1 | 1.467 | 0.8690 |
| 1 ft/s | 0.3048 | 1.097 | 0.6818 | 1 | 0.5925 |
| 1 knot | 0.5144 | 1.852 | 1.151 | 1.688 | 1 |
Pressure Conversion Chart
Quick Reference
1 atm = 101.325 kPa = 14.696 psi | 1 bar = 100 kPa | 1 atm = 760 mmHg
| Unit | Pa | kPa | bar | psi | atm | mmHg |
|---|---|---|---|---|---|---|
| 1 Pascal | 1 | 0.001 | 0.00001 | 0.000145 | 9.869×10⁻⁶ | 0.0075 |
| 1 kPa | 1,000 | 1 | 0.01 | 0.1450 | 0.009869 | 7.501 |
| 1 Bar | 100,000 | 100 | 1 | 14.50 | 0.9869 | 750.1 |
| 1 PSI | 6,895 | 6.895 | 0.06895 | 1 | 0.06805 | 51.71 |
| 1 Atmosphere | 101,325 | 101.3 | 1.013 | 14.70 | 1 | 760 |
| 1 mmHg | 133.3 | 0.1333 | 0.001333 | 0.01934 | 0.001316 | 1 |
Energy Conversion Chart
Quick Reference
1 calorie = 4.184 J | 1 BTU = 1,055 J | 1 kWh = 3,600,000 J | 1 kcal = 4,184 J
| Unit | Joule | kJ | cal | kcal | BTU | kWh |
|---|---|---|---|---|---|---|
| 1 Joule | 1 | 0.001 | 0.2390 | 0.000239 | 0.000948 | 2.778×10⁻⁷ |
| 1 Kilojoule | 1,000 | 1 | 239.0 | 0.2390 | 0.9478 | 0.000278 |
| 1 Calorie | 4.184 | 0.004184 | 1 | 0.001 | 0.003966 | 1.162×10⁻⁶ |
| 1 Kilocalorie | 4,184 | 4.184 | 1,000 | 1 | 3.966 | 0.001162 |
| 1 BTU | 1,055 | 1.055 | 252.2 | 0.2522 | 1 | 0.000293 |
| 1 kWh | 3,600,000 | 3,600 | 860,421 | 860.4 | 3,412 | 1 |
Data Storage Conversion Chart
Quick Reference
1 KB = 1,024 bytes | 1 MB = 1,024 KB | 1 GB = 1,024 MB | 1 TB = 1,024 GB
Binary (IEC) values shown — used by operating systems. Storage manufacturers often use decimal (1 KB = 1,000 bytes).
| Unit | Bytes | KB | MB | GB | TB |
|---|---|---|---|---|---|
| 1 Byte | 1 | 0.000977 | 9.537×10⁻⁷ | 9.313×10⁻¹⁰ | 9.095×10⁻¹³ |
| 1 Kilobyte | 1,024 | 1 | 0.000977 | 9.537×10⁻⁷ | 9.313×10⁻¹⁰ |
| 1 Megabyte | 1,048,576 | 1,024 | 1 | 0.000977 | 9.537×10⁻⁷ |
| 1 Gigabyte | 1,073,741,824 | 1,048,576 | 1,024 | 1 | 0.000977 |
| 1 Terabyte | 1.1×10¹² | 1,073,741,824 | 1,048,576 | 1,024 | 1 |
How to Convert Units of Measurement
Follow these four simple steps to convert between any units of measurement. This process, known as dimensional analysis, works for every type of conversion — length, weight, volume, speed, and more.
Identify Your Starting and Target Units
Determine the unit you currently have (the starting unit) and the unit you want to convert to (the target unit). Make sure both units measure the same type of quantity — you cannot convert length into weight, for example.
Find the Conversion Factor
Look up the conversion factor that relates your two units. For example, 1 mile = 1.609 kilometers. You can use the conversion charts on this page or our free online converter.
Multiply or Divide
Apply the simple rule: converting to a smaller unit → multiply; converting to a larger unit → divide. Alternatively, set up the conversion factor as a fraction so the starting units cancel out, leaving only the target units.
Check Your Answer
Verify your result makes sense. When converting to a smaller unit you should get a larger number, and vice versa. Use our online calculator to double-check your work.
Example 1
Convert 5 miles to kilometers
Conversion factor: 1 mile = 1.609 km
5 miles × 1.609 = 8.045 km
✓ Makes sense — kilometers are smaller units, so the number is larger.
Example 2
Convert 180 pounds to kilograms
Conversion factor: 1 lb = 0.4536 kg
180 lb × 0.4536 = 81.65 kg
✓ Makes sense — kilograms are larger units, so the number is smaller.
Unit Conversion in Everyday Life
Unit conversion is not just for the classroom — it shows up in countless real-world situations every day.
Cooking & Baking
International recipes often mix cups, tablespoons, grams, and milliliters. Knowing that 1 cup ≈ 236.6 mL or 1 oz ≈ 28.35 g can be the difference between a perfect cake and a flat one.
→ Cooking converterTravel & Navigation
Driving in Europe? Speed limits are in km/h (100 km/h ≈ 62 mph). Fuel economy is measured in L/100 km instead of mpg. Temperature forecasts are in Celsius.
→ Speed converterHealth & Fitness
Body weight is measured in pounds in the US and kilograms elsewhere. Medical dosages rely on precise mg and mL conversions. Knowing 1 lb = 0.4536 kg helps track progress internationally.
→ Weight converterConstruction & DIY
Lumber, flooring, and paint coverage use square feet, square meters, or square yards. International materials may list dimensions in centimeters while your plans are in inches.
→ Area converterScience & Engineering
All scientific work uses SI units (meters, kilograms, seconds). Engineers frequently convert between PSI and kPa for pressure, BTU and kWh for energy, or Newtons and pounds-force.
→ Pressure converterComputing & Data
Internet plans list speeds in Mbps, storage drives in GB or TB, and file sizes in KB or MB. Understanding that 1 GB = 1,024 MB helps you choose the right plan or device.
→ Data converterCommon Unit Conversion Mistakes (and How to Avoid Them)
- 1
Confusing US and Imperial gallons
A US gallon is 3.785 liters while an Imperial (UK) gallon is 4.546 liters — a 20% difference. The same confusion applies to pints, quarts, and fluid ounces. Always confirm which system a recipe or specification uses.
- 2
Forgetting to square or cube when converting area or volume
If 1 foot = 0.3048 meters, then 1 ft² = 0.3048² = 0.0929 m² (not 0.3048 m²). For volume the factor must be cubed: 1 ft³ = 0.3048³ = 0.02832 m³. Always raise the linear conversion factor to the appropriate power.
- 3
Multiplying when you should divide (or vice versa)
A quick sanity check: if you are converting to a smaller unit the resulting number should be larger, and the reverse is also true. If your answer goes the wrong direction, you likely used the reciprocal of the conversion factor.
- 4
Rounding too early in multi-step conversions
When chaining multiple conversion steps, keep full precision until the final result. Rounding intermediate values introduces compounding errors. Only round the final answer to the appropriate number of significant figures.
- 5
Treating temperature as a simple ratio
Unlike length or weight, temperature scales have an offset. You cannot simply multiply Fahrenheit by a factor to get Celsius — you must subtract 32 first, then multiply by 5/9. Forgetting the offset is one of the most common conversion errors.
Frequently Asked Questions About Unit Conversion
What are the 7 base SI units of measurement?
The International System of Units (SI) defines seven base units: the meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity). All other metric units — such as newtons, pascals, and watts — are derived from these seven base units.
How do you convert metric to imperial?
Multiply or divide by the appropriate conversion factor. For example, multiply inches by 2.54 to get centimeters, or divide pounds by 2.205 to get kilograms. The conversion charts above list the most common factors. For instant results, use our free online converter which handles over 750 units across 40+ categories.
What is the easiest way to convert units?
The easiest way is to use an online conversion tool like OnlineUnitConversion.com for instant, accurate results. For manual conversion, identify the conversion factor between your two units, then multiply or divide. The rule of thumb is simple: converting to a smaller unit means the number gets bigger (multiply), and converting to a larger unit means the number gets smaller (divide).
Why does the United States still use the imperial system?
The US customary system is deeply embedded in commerce, industry, and daily life. The cost of converting infrastructure, road signage, manufacturing tooling, and consumer expectations to metric has historically outweighed the perceived benefits. However, the metric (SI) system is already standard in US science, medicine, the military, and international trade.
What is the difference between mass and weight?
Mass measures the amount of matter in an object and is measured in kilograms or grams. It stays constant regardless of location. Weight measures the gravitational force acting on an object and is technically measured in newtons or pounds-force. It changes depending on gravity — you would weigh less on the Moon but have the same mass. On Earth's surface the two are proportional, which is why we use the terms interchangeably in everyday conversation.
How do you convert temperature between Fahrenheit and Celsius?
To convert °F to °C: subtract 32, then multiply by 5/9. To convert °C to °F: multiply by 9/5 (or 1.8), then add 32. For example, 72 °F = (72 − 32) × 5/9 = 22.2 °C. Unlike most unit conversions, temperature conversions use an offset — not just a multiplicative ratio — because the Fahrenheit and Celsius scales have different zero points.
Start Converting Units Now
Unit conversion does not have to be complicated. With the charts on this page you can quickly look up any common conversion factor, and with our free online calculator you can convert between over 750 units across 40+ categories in an instant. Bookmark this page to keep it at your fingertips whenever you need it.