Conversion Calculator: Convert Length, Weight, Temperature, Area & Volume Units

  • Adam
  • November 5, 2025

Free online conversion calculator for metric, US customary, and imperial units. Convert length, weight, temperature, area, and volume with high precision and instant results.

Conversion Calculator

Convert Between Metric, US Customary & Imperial Units

📐 Pro Tips for Accurate Conversions: Select correct unit category (area ≠ volume). Double-check source and target units before converting. For temperature, note different scale starting points. Metric (SI) based on powers of 10. US customary remains common in US. Most conversions rounded to practical precision.

Length Converter

Common Conversions: 1 inch = 2.54 cm | 1 foot = 12 inches | 1 yard = 3 feet | 1 mile = 1.60934 km | 1 meter = 39.3701 inches
✅ Conversion Result:

Weight/Mass Converter

Common Conversions: 1 pound = 453.592 g | 1 ounce = 28.3495 g | 1 kg = 2.20462 lb | 1 stone = 14 pounds | 1 metric ton = 1000 kg
✅ Conversion Result:

Temperature Converter

Temperature Formulas: °F = (°C × 9/5) + 32 | °C = (°F - 32) × 5/9 | K = °C + 273.15 | Note: Temperature has offset, not proportional
✅ Conversion Result:

Area Converter

Common Conversions: 1 m² = 10.7639 ft² | 1 acre = 4046.86 m² | 1 hectare = 10,000 m² | 1 km² = 100 hectares
✅ Conversion Result:

Volume Converter

Common Conversions: 1 L = 1000 ml | 1 L = 0.264172 gal | 1 m³ = 1000 L | 1 ft³ = 28.3168 L | 1 gal = 3.78541 L
✅ Conversion Result:
📊 Different Systems of Units
Metric System (SI - International System):

Decimal-based (powers of 10). Standardized internationally. Used in science, medicine, most countries. Base units: meter (length), kilogram (mass), second (time), Celsius (temperature). Advantages: logical relationships, easy conversions, universal standardization.

US Customary Units:

Primarily used in United States. Based on historical standards. Length: inches, feet, yards, miles. Weight: ounces, pounds. Volume: cups, pints, gallons. Complex relationships (12 inches = 1 foot, 5280 feet = 1 mile). Disadvantage: non-decimal relationships.

Imperial Units:

Used in UK and Commonwealth countries. Similar to US customary with some differences. Example: Imperial gallon ≠ US gallon. Gradually replaced by metric but still used informally (height in feet/inches, weight in stones/pounds).

Historical Evolution:

Early units based on body measurements: inch (thumb width), foot (foot length), yard (arm span). Arbitrary and inconsistent. Different regions used different standards. Trade difficulties led to metric system creation (1790s France). SI adopted internationally (1960).

Why Multiple Systems Coexist:

Cultural tradition: US invested in imperial infrastructure. Cost of conversion: expensive to change industrial systems. Public familiarity: people comfortable with familiar units. Specific industries: aviation uses feet, medicine uses metric. Gradual transition ongoing globally.

📋 Quick Conversion Reference
Length Conversions:
1 inch 2.54 cm
1 foot 30.48 cm = 12 inches
1 yard 0.9144 m = 3 feet
1 mile 1.60934 km = 5280 feet
1 meter 39.3701 inches
Weight Conversions:
1 ounce 28.3495 grams
1 pound 453.592 grams = 16 ounces
1 stone 6.35029 kg = 14 pounds
1 kilogram 2.20462 pounds
Temperature Key Points:
  • Water freezes: 0°C = 32°F = 273.15K
  • Room temperature: ~20°C = 68°F = 293.15K
  • Body temperature: 37°C = 98.6°F = 310.15K
  • Water boils: 100°C = 212°F = 373.15K
  • Absolute zero: -273.15°C = -459.67°F = 0K
Area Conversions:
1 m² 10.7639 ft²
1 hectare 10,000 m² = 2.47105 acres
1 acre 4046.86 m²
Volume Conversions:
  • 1 liter = 1000 milliliters (ml)
  • 1 US gallon = 3.78541 liters
  • 1 cubic meter = 1000 liters
  • 1 fluid ounce (US) = 29.5735 milliliters
❓ Frequently Asked Questions
What's the difference between mass and weight? +
Mass: amount of matter (measured in kg or g). Constant everywhere. Weight: force of gravity on mass (measured in Newtons). Varies by location (moon ≠ Earth). On Earth surface: proportional relationship. This calculator treats as equivalent for practical daily use.
Why can't I convert area to volume directly? +
Different dimensions. Area measures 2D surface (m²). Volume measures 3D space (m³). Require depth/height for conversion. Example: 1 m² doesn't equal 1 m³. Need to know thickness/depth. Use appropriate calculator section for each.
Is Celsius or Kelvin better for conversions? +
Celsius: everyday use, water freezes at 0°C, boils at 100°C. Kelvin: scientific use, absolute zero reference (0K), linear scale. Fahrenheit: US weather temperatures. Temperature conversion requires offset (not just multiplication). Careful with formula used.
Why are there different pounds and gallons? +
Historical evolution. US adopted own standards (US customary). UK uses imperial. Different measures: 1 US gallon ≠ 1 imperial gallon (3.78 L vs 4.54 L). Avoirdupois pound (weight) vs troy pound (precious metals). Always specify which system.
How precise should my conversions be? +
Depends on use. Cooking: ±10% acceptable. Tailoring: ±2% needed. Engineering: ±0.01% required. Science: ±0.001% better. Calculator provides high precision (15+ decimals). Round results appropriately for your application. More precision doesn't always mean better result.
Why is 1 pound exactly 453.592 grams? +
International standard (1959). Pound defined as exactly 0.45359237 kilograms. Precise legal definition ensures consistency worldwide. Historical origin: pound based on weight of grain. Modern definition: standardized for international trade and science.
Are metric conversions always 10-based? +
Yes, metric (SI) system 10-based: milli- (1/1000), centi- (1/100), kilo- (1000), mega- (1,000,000). Logical progression. Makes conversions easy (just move decimal point). Advantage over US customary: 12 inches ≠ 10 inches. Disadvantage: must learn metric prefixes.
What's the advantage of the metric system? +
Decimal-based: logical progression. Interrelated: 1 cm³ water = 1 gram = 1 milliliter. International standardization. Easy calculations (no fractions). Scientific accuracy. Used globally. Disadvantage: unfamiliar to some (US tradition). Historical: established 1790, adopted 1960 (SI).

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