How do I convert meters to feet?

Multiply meters by 3.28084 to get feet. Example: 5 meters × 3.28084 = 16.4042 feet. To convert feet back to meters, divide by 3.28084 (or multiply by 0.3048). Our calculator does this instantly — select Length category, choose meters → feet, enter your value.

How do I convert Celsius to Fahrenheit?

Use the formula: °F = (°C × 9/5) + 32. Example: 25°C × 1.8 + 32 = 77°F. To convert Fahrenheit to Celsius: °C = (°F − 32) × 5/9. Temperature is the only common conversion that uses a formula rather than a simple multiplication factor, because the scales have different zero points.

How do I convert kilograms to pounds?

Multiply kilograms by 2.20462 to get pounds. Example: 70 kg × 2.20462 = 154.32 lbs. To convert pounds to kilograms, divide by 2.20462 (or multiply by 0.453592). One kilogram equals approximately 2.2 pounds — a useful mental shortcut.

What is the difference between US and UK gallons?

A US gallon equals 3.78541 liters. A UK (Imperial) gallon equals 4.54609 liters — about 20% larger. This difference matters in fuel calculations, recipe scaling, and industrial measurements. Our calculator uses US gallons by default. When converting from UK gallons, select 'Imperial Gallon' from the dropdown.

How do I convert miles to kilometers?

Multiply miles by 1.60934 to get kilometers. Example: 60 miles × 1.60934 = 96.56 km. To convert km to miles, divide by 1.60934 (or multiply by 0.621371). A quick mental approximation: multiply miles by 1.6 for kilometers, or multiply km by 0.6 for miles.

What is a hectare and how does it compare to acres?

A hectare (ha) is 10,000 square meters — a square 100m × 100m. One hectare equals 2.47105 acres. Hectares are the standard unit for land area in metric countries; acres are used in the US and UK. A football field is approximately 0.45 hectares (1.1 acres).

How do I convert mph to km/h?

Multiply mph by 1.60934 to get km/h. Example: 60 mph × 1.60934 = 96.56 km/h. The conversion factor is the same as miles to kilometers, because speed is distance per time. A quick approximation: multiply mph by 1.6 for km/h, or multiply km/h by 0.62 for mph.

What is Kelvin and when is it used?

Kelvin (K) is the SI base unit for temperature used in science and engineering. It starts at absolute zero (−273.15°C), the lowest possible temperature. To convert Celsius to Kelvin: K = °C + 273.15. Kelvin has no negative values, making it convenient for thermodynamics equations. Normal room temperature is approximately 293–298 K (20–25°C).

How do I convert PSI to bar?

Multiply PSI by 0.0689476 to get bar. Example: 30 PSI × 0.0689476 = 2.07 bar. To convert bar to PSI, multiply by 14.5038. Standard tire pressure in the US is commonly expressed in PSI (around 32–35 PSI for passenger cars), while European vehicles typically use bar (2.2–2.4 bar).

What is the metric system and how does it work?

The metric system (formally the International System of Units, SI) is a decimal-based measurement system where all units scale by powers of 10. For example: 1 kilometer = 1,000 meters; 1 meter = 100 centimeters = 1,000 millimeters. This consistent decimal scaling makes conversions within the system trivially simple — just move the decimal point.

Length · Weight · Temp · Volume · Area · Speed · Time · Pressure

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Common Conversion Factors

The most-used conversions at a glance.

Category	Conversion Factor	Example	Reverse
Miles → km	× 1.60934	60 mi = 96.56 km	÷ 1.60934
kg → lbs	× 2.20462	70 kg = 154.32 lbs	÷ 2.20462
°C → °F	× 9/5 + 32	25°C = 77°F	(°F−32) × 5/9
Liters → US gal	÷ 3.78541	10 L = 2.642 gal	× 3.78541
sq m → sq ft	× 10.7639	20 m² = 215.3 ft²	÷ 10.7639
mph → km/h	× 1.60934	60 mph = 96.56 km/h	÷ 1.60934
Meters → feet	× 3.28084	5 m = 16.40 ft	÷ 3.28084
Hectares → acres	× 2.47105	1 ha = 2.471 acres	÷ 2.47105
PSI → bar	× 0.0689476	30 PSI = 2.07 bar	÷ 0.0689476
°C → Kelvin	+ 273.15	25°C = 298.15 K	− 273.15

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The NASA $125M Mistake — Why Conversions Matter

In 1999, NASA's Mars Climate Orbiter was destroyed because one engineering team used metric units (newtons) and another used imperial (pound-force). The mismatch caused a trajectory error that sent the spacecraft into the Martian atmosphere. Accurate unit conversion isn't just academic — it's mission-critical.

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Metric vs Imperial

The metric system (SI) is decimal-based — all units scale by powers of 10. 1 km = 1,000 m = 100,000 cm. This makes mental arithmetic simple and is used by 195+ countries for science, trade, and everyday life.

The US customary system uses non-decimal scaling: 12 inches per foot, 3 feet per yard, 1,760 yards per mile. The US remains one of only three countries (with Myanmar and Liberia) not officially using the metric system.

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Temperature Scales Explained

Celsius (°C): Water freezes at 0°C, boils at 100°C. Used everywhere except the US for everyday temperature.

Fahrenheit (°F): Water freezes at 32°F, boils at 212°F. Used in the US for weather and cooking.

Kelvin (K): Starts at absolute zero (−273.15°C). No negative values. Used in science and engineering. The only scale where "twice as hot" has true physical meaning.

How Unit Conversion Works

Unit conversion is the process of expressing a measurement in a different unit of the same physical quantity. All conversions within a category use a fixed mathematical relationship — either a multiplication factor (for most units) or a formula (for temperature scales, which have different zero points).

Multiplicative Conversions (Most Units)

For length, weight, volume, area, speed, time, and pressure, conversion is a simple multiplication. Every unit can be expressed as a fixed ratio to a base unit (the SI base unit for that category). To convert from unit A to unit B: multiply by (A's SI factor ÷ B's SI factor).

Example: meters to feet Base: 1 meter (SI base for length) 1 foot = 0.3048 meters meters → feet: value × (1 ÷ 0.3048) = value × 3.28084 feet → meters: value × 0.3048 Example: 5 meters → feet 5 × 3.28084 = 16.4042 feet Area conversions use the square of the linear factor: 1 sq meter = 10.7639 sq feet (3.28084²)

Temperature Conversions (Formula-Based)

Temperature scales have different zero points, so a simple multiplication factor doesn't work. Each conversion requires a two-step formula:

Celsius → Fahrenheit: °F = (°C × 9/5) + 32 Fahrenheit → Celsius: °C = (°F − 32) × 5/9 Celsius → Kelvin: K = °C + 273.15 Kelvin → Celsius: °C = K − 273.15 Fahrenheit → Kelvin: K = (°F − 32) × 5/9 + 273.15 Key reference points: Absolute zero: −273.15°C = −459.67°F = 0 K Water freezes: 0°C = 32°F = 273.15 K Body temperature:37°C = 98.6°F = 310.15 K Water boils: 100°C = 212°F = 373.15 K

Common Conversion Categories — Reference Guide

Length & Distance

Length is the most commonly converted measurement. The SI base unit is the meter. Common conversions include meters ↔ feet (factor: 3.28084), kilometers ↔ miles (factor: 1.60934), and centimeters ↔ inches (factor: 0.393701). The inch was officially defined as exactly 25.4mm in 1959, making all US customary length conversions exact by definition.

Weight & Mass

The SI unit is the kilogram. 1 kg = 2.20462 lbs = 35.274 oz. Note: technically "weight" in physics means force (newtons), while "mass" means the amount of matter (kilograms). In everyday use, weight and mass are used interchangeably at Earth's surface. A US ton = 2,000 lbs; a metric tonne = 1,000 kg ≈ 2,204.6 lbs; a UK (long) ton = 2,240 lbs.

Volume

The SI unit is the cubic meter (m³). Liters (L) are 1/1000 of a cubic meter. 1 US gallon = 3.78541 L; 1 UK imperial gallon = 4.54609 L — a 20% difference that causes confusion in fuel calculations. 1 US fluid ounce = 29.5735 mL; 1 UK fluid ounce = 28.4131 mL.

Pressure

The SI unit is the pascal (Pa). Common units include bar (100,000 Pa), PSI (pound per square inch, 6,894.76 Pa), and standard atmosphere (atm, 101,325 Pa). Tire pressure in the US is typically 30–35 PSI (2.07–2.41 bar). Standard atmospheric pressure at sea level is 1 atm = 14.696 PSI = 1.01325 bar.

Frequently Asked Questions

Multiply meters by 3.28084. Example: 5 meters × 3.28084 = 16.4042 feet. To convert back: feet × 0.3048 = meters. Quick mental shortcut: multiply meters by 3.3 for a rough estimate. Use our calculator above — select Length, choose meters → feet, type your value.

Formula: °F = (°C × 9/5) + 32. Example: 25°C × 1.8 + 32 = 77°F. Reverse: °C = (°F − 32) × 5/9. Quick mental shortcut: double the Celsius, subtract 10%, add 32. For 20°C: 40 − 4 + 32 = 68°F (actual: 68°F ✓).

Multiply kg by 2.20462. Example: 70 kg × 2.20462 = 154.32 lbs. Reverse: lbs × 0.453592 = kg. Quick approximation: multiply kg by 2.2. Example: 80 kg ≈ 176 lbs (actual: 176.37 lbs).

US gallon = 3.78541 liters. UK (Imperial) gallon = 4.54609 liters — about 20% larger. This difference matters in fuel economy comparisons. A car getting 30 MPG in the UK uses different fuel volumes than one getting 30 MPG in the US. Our calculator uses US gallons by default.

Multiply miles by 1.60934. Example: 60 miles × 1.60934 = 96.56 km. Reverse: km × 0.621371 = miles. Quick approximation: multiply miles by 1.6. A 100-mile journey is approximately 160 km; a 5K race is 3.1 miles.

A hectare (ha) = 10,000 m² — a 100m × 100m square. 1 hectare = 2.47105 acres. A football field is approximately 0.45 ha (1.1 acres). Hectares are the standard metric land unit; acres are used in the US and UK. 1 square kilometer = 100 hectares = 247.1 acres.

Multiply mph by 1.60934. This is the same factor as miles to km, since speed is just distance per time. Example: 60 mph × 1.60934 = 96.56 km/h. Reverse: km/h × 0.621371 = mph. Highway speed limits: US 65 mph ≈ 105 km/h; typical EU 130 km/h ≈ 81 mph.

Kelvin (K) is the SI temperature unit starting at absolute zero (−273.15°C). There are no negative Kelvin values. Kelvin = °C + 273.15. Used in thermodynamics, chemistry, and physics because equations involving temperature ratios only work correctly with an absolute scale. Room temperature ≈ 293–298 K.

Multiply PSI by 0.0689476 to get bar. Example: 32 PSI × 0.0689476 = 2.21 bar. Reverse: bar × 14.5038 = PSI. Car tire pressure in the US is typically 32–35 PSI (2.2–2.4 bar). Standard atmospheric pressure = 14.696 PSI = 1.01325 bar = 101,325 Pa.

The metric system (SI — International System of Units) is a decimal-based measurement system used in 195+ countries. All units scale by powers of 10 — kilo = ×1,000; centi = ×0.01; milli = ×0.001. This makes within-system conversions trivial (just move the decimal). The US remains one of only three countries (with Myanmar and Liberia) not officially using metric as its primary system.

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