Metric Conversion Calculator
Convert between metric and imperial units across six categories — length, weight, volume, temperature, speed, and area. Select a category in the panel on the left, enter your value, choose your units, and get an instant result. Supports kilometers, miles, kilograms, pounds, liters, gallons, Celsius, Fahrenheit, and more.
What Is a Metric Conversion Calculator?
A metric conversion calculator is a universal unit converter that translates measurements between the metric system (SI units) and other systems — primarily the US customary and Imperial systems. It covers the most commonly needed measurement categories: length (kilometers, meters, miles, feet), weight and mass (kilograms, grams, pounds, ounces), volume (liters, milliliters, gallons, cups), temperature (Celsius, Fahrenheit, Kelvin), speed (km/h, mph, m/s), and area (square meters, acres, hectares, square feet).
Metric conversions are needed every day — when traveling internationally, following recipes from other countries, understanding weather forecasts, reading scientific papers, comparing vehicle fuel efficiency, or purchasing land. The converter on the left handles all six categories with instant results. If you specifically need to convert metric units to US standard units (mm to inches, kg to pounds, liters to gallons, °C to °F), the dedicated metric to standard converter focuses on that direction with full conversion tables. For specialized liquid volume conversions, see the liquid measurement converter. For cooking-specific weight and volume conversions, see the cooking measurement converter.
How the Metric Conversion Calculator Works
Selecting a Category
Start by choosing a measurement category from the dropdown: Length, Weight/Mass, Volume, Temperature, Speed, or Area. The From and To unit dropdowns update to show only units relevant to that category. This prevents incompatible conversions (such as trying to convert kilometers to kilograms) and keeps the interface focused on what you need.
Choosing From and To Units
After selecting a category, choose the unit you are converting from and the unit you want to convert to. Enter the numeric value in the Value field. For most categories (length, weight, volume, speed, area), the conversion is done by converting to a base unit (meters, grams, milliliters, m/s, or m²) and then to the target unit. Temperature is handled with its own formulas since it uses offset scales, not simple multiplication factors.
Reading the Result
Click Convert to see the result displayed as a chat bubble with the full conversion shown. You can then type follow-up questions directly into the chat — for example, asking for the formula, requesting additional related conversions, or asking how the converted value compares to a real-world reference. Previous conversion results are included as context when you ask follow-up questions, so the AI understands what you converted.
The Metric System Explained
Base Units: Meter, Gram, Liter
The metric system (formally the International System of Units, or SI) is built on seven base units, three of which are most commonly used in everyday conversions. The meter (m) is the base unit of length — defined since 1983 as the distance light travels in 1/299,792,458 of a second. The gram (g) is the base unit of mass, though in practice the kilogram (kg, equal to 1000 grams) is used more commonly and is technically the SI base unit. The liter (L) is not formally an SI base unit but is a widely accepted metric unit of volume, equal to 1 cubic decimeter (1000 cm³).
Metric Prefixes: Kilo, Centi, Milli, Micro
One of the metric system's greatest strengths is its consistent prefix system. Each prefix represents a power of ten, making conversions between metric units straightforward multiplication or division.
| Prefix | Symbol | Factor | Example |
|---|---|---|---|
| giga | G | 10⁹ (1,000,000,000) | 1 Gm = 1 billion meters |
| mega | M | 10⁶ (1,000,000) | 1 Mm = 1 million meters |
| kilo | k | 10³ (1,000) | 1 km = 1,000 meters |
| hecto | h | 10² (100) | 1 hm = 100 meters |
| deca | da | 10¹ (10) | 1 dam = 10 meters |
| (base) | 10⁰ (1) | meter, gram, liter | |
| deci | d | 10⁻¹ (0.1) | 1 dm = 0.1 meters |
| centi | c | 10⁻² (0.01) | 1 cm = 0.01 meters |
| milli | m | 10⁻³ (0.001) | 1 mm = 0.001 meters |
| micro | μ | 10⁻⁶ (0.000001) | 1 μm = 0.000001 meters |
| nano | n | 10⁻⁹ | 1 nm = 0.000000001 meters |
Why the Metric System Is Used Worldwide
The metric system is the official measurement system in 195 of the world's 197 countries. Only the United States, Liberia, and Myanmar have not officially adopted it as their primary system, though all three use metric units in science, medicine, and international trade. The metric system's adoption is driven by its base-10 structure, which eliminates the need to memorize arbitrary conversion factors (like 12 inches per foot or 5280 feet per mile) and makes calculations much simpler. International science, engineering, and medicine operate almost exclusively in SI units regardless of national measurement conventions.
Metric Conversion Charts
Length Conversion Chart
| Unit | km | m | cm | mile | foot | inch |
|---|---|---|---|---|---|---|
| 1 kilometer | 1 | 1,000 | 100,000 | 0.6214 | 3,280.84 | 39,370.1 |
| 1 meter | 0.001 | 1 | 100 | 0.000621 | 3.28084 | 39.3701 |
| 1 centimeter | 0.00001 | 0.01 | 1 | 0.0000062 | 0.032808 | 0.393701 |
| 1 mile | 1.60934 | 1,609.34 | 160,934 | 1 | 5,280 | 63,360 |
| 1 foot | 0.000305 | 0.3048 | 30.48 | 0.000189 | 1 | 12 |
| 1 inch | 0.0000254 | 0.0254 | 2.54 | 0.0000158 | 0.08333 | 1 |
Weight Conversion Chart
| Unit | kg | g | lb | oz | stone |
|---|---|---|---|---|---|
| 1 kilogram | 1 | 1,000 | 2.20462 | 35.274 | 0.15747 |
| 1 gram | 0.001 | 1 | 0.002205 | 0.035274 | 0.000157 |
| 1 pound | 0.453592 | 453.592 | 1 | 16 | 0.071429 |
| 1 ounce | 0.028350 | 28.3495 | 0.0625 | 1 | 0.004464 |
| 1 stone | 6.35029 | 6,350.29 | 14 | 224 | 1 |
| 1 tonne | 1,000 | 1,000,000 | 2,204.62 | 35,274 | 157.47 |
Volume Conversion Chart
| Unit | L | mL | US gal | US qt | US fl oz |
|---|---|---|---|---|---|
| 1 liter | 1 | 1,000 | 0.26417 | 1.05669 | 33.814 |
| 1 milliliter | 0.001 | 1 | 0.000264 | 0.001057 | 0.033814 |
| 1 US gallon | 3.78541 | 3,785.41 | 1 | 4 | 128 |
| 1 US quart | 0.946353 | 946.353 | 0.25 | 1 | 32 |
| 1 US cup | 0.236588 | 236.588 | 0.0625 | 0.25 | 8 |
| 1 US fl oz | 0.029574 | 29.5735 | 0.0078125 | 0.03125 | 1 |
Temperature Conversion Chart
| Reference | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20 | 68 | 293.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Water boils | 100 | 212 | 373.15 |
| Oven (moderate) | 180 | 356 | 453.15 |
| Oven (hot) | 230 | 446 | 503.15 |
Temperature conversion formulas: °C to °F = (°C × 9/5) + 32 | °F to °C = (°F − 32) × 5/9 | °C to K = °C + 273.15
Common Metric Conversions
Everyday Length Conversions
The most frequently needed length conversions involve kilometers and miles for travel, and centimeters and inches for personal measurements and product sizing. Key reference points: 1 kilometer = 0.6214 miles (roughly 5/8 of a mile), 1 mile = 1.609 km, 1 meter = 3.281 feet = 39.37 inches, 1 centimeter = 0.394 inches, 1 inch = 2.54 cm exactly. For distance on road signs and speedometers, the quick mental approximation is to multiply km by 0.6 to get miles (actual factor is 0.6214). See our miles converter for a dedicated miles-to-km conversion tool with full tables.
Kitchen and Cooking Conversions
Kitchen conversions span both weight and volume. The most common: 1 kg = 2.205 lb, 100 g = 3.527 oz, 1 liter = 4.227 US cups, 1 liter = 33.814 fl oz, 1 cup = 236.6 mL, 1 tbsp = 14.79 mL. Oven temperatures require Fahrenheit-to-Celsius conversions for US vs. international recipes: 350°F = 177°C, 375°F = 190°C, 400°F = 204°C, 425°F = 218°C. For ingredient-specific volume-to-weight conversions (like cups of flour to grams), use the cooking measurement converter.
Fitness and Health Conversions
Body weight is commonly expressed in kilograms in most countries and pounds in the US. Key conversions: 1 kg = 2.2046 lb, 50 kg = 110.2 lb, 70 kg = 154.3 lb, 80 kg = 176.4 lb, 100 kg = 220.5 lb. Height conversions between centimeters and feet/inches: 150 cm = 4'11", 160 cm = 5'3", 170 cm = 5'7", 175 cm = 5'9", 180 cm = 5'11", 190 cm = 6'3". Running distances: 5K = 3.107 miles, 10K = 6.214 miles, half marathon = 21.097 km = 13.109 miles, marathon = 42.195 km = 26.219 miles.
Metric Conversion Examples
Example 1 — Convert 5 km to Miles
Calculation: 5 km × 0.621371 mi/km = 3.10686 miles. So a 5 km race is approximately 3.1 miles. The conversion factor from km to miles is 0.621371 (or equivalently, 1 mile = 1.60934 km). For a quick mental approximation, multiply km by 0.6: 5 × 0.6 = 3.0 miles (actual is 3.107). This 5K distance is the most common recreational race distance worldwide.
Example 2 — Convert 75 kg to Pounds
Calculation: 75 kg × 2.20462 lb/kg = 165.347 lb. So a person weighing 75 kg weighs approximately 165.3 pounds. The conversion factor from kg to pounds is exactly 2.20462 (1 lb = 0.453592 kg). For quick mental math, multiply kg by 2.2: 75 × 2.2 = 165 pounds — very close to the exact value. In stone (used in the UK for body weight), 75 kg = 11 stone 11.3 pounds.
Example 3 — Convert 350°F to Celsius
Calculation: (350 − 32) × 5/9 = 318 × 5/9 = 1590/9 = 176.67°C. So an oven set to 350°F is approximately 177°C, which is a common moderate baking temperature. Unlike length and weight, temperature cannot be converted with a simple multiplication factor because the Fahrenheit and Celsius scales have different zero points. The formula °C = (°F − 32) × 5/9 is exact. In Kelvin: 176.67 + 273.15 = 449.82 K.
Frequently Asked Questions
What is the metric system?
The metric system (officially the International System of Units, or SI) is a decimal-based measurement system built around consistent base units: the meter (length), kilogram (mass), liter (volume), second (time), kelvin (temperature), ampere (electric current), and candela (luminous intensity). Every unit is a power of 10 multiple of the base unit, making calculations straightforward. It was developed in France in the 1790s and is now the official measurement system in virtually every country worldwide.
How do I convert metric to imperial?
Each metric-to-imperial conversion uses a specific multiplication factor. The most common: multiply km by 0.621 to get miles, multiply kg by 2.205 to get pounds, multiply liters by 0.264 to get US gallons, subtract 32 and multiply by 5/9 to convert °F to °C, and multiply m² by 10.764 to get ft². Use the calculator above to handle any combination instantly without memorizing formulas.
What countries use the metric system?
All but three countries officially use the metric system: the United States, Liberia, and Myanmar still use customary measurement systems for everyday life. However, all three countries use metric units in science, medicine, military, and international trade. The US has made several attempts to fully convert to metric since the 1970s but has not completed the transition. Most US products display both metric and imperial measurements on packaging.
What are the metric prefixes?
Metric prefixes indicate powers of 10. The most common: kilo (k) = 1,000×, mega (M) = 1,000,000×, giga (G) = 1,000,000,000×, hecto (h) = 100×, deca (da) = 10×, deci (d) = 1/10, centi (c) = 1/100, milli (m) = 1/1,000, micro (μ) = 1/1,000,000, nano (n) = 1/1,000,000,000. For example, 1 kilometer = 1,000 meters, 1 centimeter = 0.01 meters, and 1 milliliter = 0.001 liters.
Why doesn't the US use the metric system?
The US retained its customary measurement system largely due to historical inertia, economic switching costs, and political resistance. The US was one of the first countries to standardize measurements nationally (using the British imperial system it inherited from colonial rule), and by the time metrication became widespread internationally, the US had decades of infrastructure, tooling, consumer habits, and legal standards built around customary units. The Metric Conversion Act of 1975 made metric the preferred system but did not mandate it, leaving conversion voluntary. Cultural familiarity and cost of transition continue to delay full adoption.