Unit Converter - Length, Weight, Temperature & More

Formula

Value in Target Unit = Value in Source Unit × (Target Factor / Source Factor)

Convert through a base unit. Divide by the source factor to get the base value, then multiply by the target factor. Temperature requires special formulas due to offset scales.

Worked Examples

Example 1: Recipe Conversion

Problem:A European recipe calls for 500 grams of flour. How many cups is that?

Solution:500 grams of flour ≈ 4 cups (all-purpose flour) Note: Cup measurements vary by ingredient: - Flour: ~125g per cup - Sugar: ~200g per cup - Butter: ~227g per cup For precision, weight measurements are preferred.

Result:500g flour ≈ 4 cups

Example 2: Travel Speed Conversion

Problem:A car is traveling at 120 km/h. What is that in mph?

Solution:Conversion factor: 1 km/h = 0.621371 mph 120 km/h × 0.621371 = 74.56 mph Alternatively: 120 ÷ 1.60934 = 74.56 mph

Result:120 km/h = 74.56 mph

Example 3: Real Estate Area

Problem:A property listing shows 2,000 square feet. What is that in square meters?

Solution:Conversion: 1 sq ft = 0.092903 sq m 2,000 sq ft × 0.092903 = 185.8 sq m Or: 2,000 ÷ 10.764 = 185.8 sq m This is equivalent to about 1.86 are or 0.0186 hectares.

Result:2,000 sq ft = 185.8 sq m

Frequently Asked Questions

How do I convert between different units?

Select the category (length, weight, temperature, etc.), enter your value, and choose the 'from' and 'to' units. The converter instantly shows the result. You can also see a complete conversion table showing your value in all units of that category.

How do I convert meters to feet?

1 meter = 3.28084 feet. To convert, multiply meters by 3.28084. For example, 5 meters × 3.28084 = 16.4042 feet. Or divide feet by 3.28084 to get meters. The converter handles this automatically.

What is Kelvin and when is it used?

Kelvin is the SI unit of temperature, used in science. It starts at absolute zero (-273.15°C), the coldest possible temperature. To convert: K = °C + 273.15. There are no negative Kelvin values. Room temperature (20°C) = 293.15K.

What's the difference between mass and weight?

Mass measures the amount of matter (constant everywhere) in kilograms. Weight is the force of gravity on mass (varies by location) in Newtons. On Earth, we use them interchangeably, but in physics and space, they differ significantly.

What is the difference between mass and weight?

Mass measures the amount of matter in an object (kilograms) and is constant everywhere. Weight is the gravitational force on that mass (newtons) and varies by location. On Earth, a 1 kg object weighs about 9.8 newtons. In everyday use, the terms are often used interchangeably.

How do significant figures affect unit conversions?

Your converted result should have the same number of significant figures as your original measurement. If you measure 5.2 inches (2 significant figures), converting to centimeters gives 13 cm, not 13.208 cm. Using excessive decimal places implies false precision.

When should I use metric vs imperial units?

Use metric for science, medicine, international communication, and precision work. Use imperial when required by local convention (US construction, cooking, road signs). Engineering increasingly uses metric. Always match the unit system expected by your audience or industry.

What are the most common unit conversion mistakes?

Common errors include confusing fluid ounces with weight ounces, mixing up miles and nautical miles, forgetting that UK and US gallons differ (UK is 20% larger), using the wrong temperature formula, and not accounting for the difference between troy and avoirdupois ounces.

What is the origin of common measurement units?

A foot was originally based on the length of a human foot. A yard was the distance from nose to outstretched fingertip. A mile comes from the Roman mille passus (1,000 paces). The meter was defined as one ten-millionth of the distance from equator to pole.

How do I convert between fluid volume units?

Key conversions: 1 gallon = 4 quarts = 8 pints = 128 fluid ounces = 3.785 liters. 1 liter = 1,000 milliliters = 33.814 fluid ounces. 1 cup = 8 fluid ounces = 236.6 milliliters. Note that US and imperial gallons are different sizes.

Background & Theory

Unit conversion is the process of expressing a quantity in different units while maintaining the same value. Understanding conversion fundamentals helps in science, engineering, cooking, travel, and daily life. **Metric (SI) System:** Based on powers of 10: - kilo- (k) = 1,000 - hecto- (h) = 100 - deka- (da) = 10 - base unit = 1 - deci- (d) = 0.1 - centi- (c) = 0.01 - milli- (m) = 0.001 - micro- (μ) = 0.000001 **Common Conversion Factors:** **Length:** - 1 inch = 2.54 cm (exact) - 1 foot = 30.48 cm - 1 yard = 0.9144 m - 1 mile = 1.60934 km **Weight:** - 1 ounce = 28.3495 g - 1 pound = 453.592 g - 1 kg = 2.20462 lb **Volume:** - 1 fluid oz = 29.5735 mL - 1 cup = 236.588 mL - 1 gallon (US) = 3.78541 L **Temperature Formulas:** - °F = (°C × 9/5) + 32 - °C = (°F - 32) × 5/9 - K = °C + 273.15 - °R = (°C + 273.15) × 9/5 **Conversion Process:** 1. **Identify units:** Source and target 2. **Find conversion factor:** Ratio between units 3. **Multiply or divide:** Depending on direction 4. **Check reasonableness:** Does answer make sense? **Dimensional Analysis:** Units can be treated algebraically: 5 km × (1000 m / 1 km) = 5000 m The km units cancel, leaving meters. **Common Mistakes:** 1. Squaring linear factors for area (wrong) 2. Cubing linear factors for volume (wrong) 3. Confusing mass and weight 4. Mixing US and UK gallons 5. Temperature: additive shift, not just ratio **Tips for Accuracy:** - Use exact conversion factors when known - Carry extra decimal places during calculation - Round only the final answer - Double-check by converting back - Note which measurement system (US/UK/SI)

History

Unit systems have developed throughout human history, often based on human body measurements or natural phenomena. The Egyptian cubit (length of forearm) and the Roman foot (pes) are ancient examples still reflected in modern units. The metric system was born during the French Revolution (1790s), designed as a rational, decimal-based system. The meter was originally defined as one ten-millionth of the distance from the North Pole to the equator. The kilogram was defined by a platinum-iridium cylinder kept in Paris. The British Imperial system codified in 1824 formalized English units. The United States customary units diverged slightly from Imperial measures, creating the US/UK gallon distinction that persists today. In 1960, the International System of Units (SI) was established, modernizing and standardizing the metric system. The seven SI base units (meter, kilogram, second, ampere, kelvin, mole, candela) form the foundation of modern measurement. In 2019, all SI units were redefined based on fundamental physical constants rather than physical artifacts. The kilogram is now defined by the Planck constant, ensuring measurement standards that are universal, unchanging, and reproducible anywhere. Today, only three countries (US, Myanmar, Liberia) haven't officially adopted the metric system, though metric is used in science and international trade worldwide. Digital converters make translation between systems instantaneous.