Unit Converter

Inches ↔ Millimeters:
1 in = 25.4 mm. Inches accept fractions (e.g. 3/16, 1 1/2). Use when: drill bits, sheet metal, PCB traces, US/imperial specs.

Kilometers ↔ Miles:
1 km = 0.621371 mi. Use when: road signs, odometers, running/cycling distances, aviation (nm is different).

Meters ↔ Feet:
1 m = 3.28084 ft. Use when: room dimensions, ceiling height, runway length, altitude in feet.

• 1 m² = 10.7639 sq ft
• 1 Acre = 43,560 sq ft (≈ 4,046 m²)
• 1 Hectare = 10,000 m² (≈ 2.47 acres)

Sq meters/feet for floors and walls; acres/hectares for land, farms, and real estate.

• 1 m³ = 1000 L
• 1 L ≈ 33.814 US fl oz
• 1 US gal = 128 US fl oz ≈ 3.785 L

Cubic meters for solids and large capacities; Liters for fuel and lab work; fl oz for drinks and recipes; gallons for tanks and fuel economy (US).

US fluid measures; UK Imperial differs slightly.

• 1 kg = 1000 g ≈ 2.20462 lbs
• 1 lb = 16 oz = 453.59237 g
• 1 oz (avoirdupois) = 28.3495 g
• 1 ozt (troy) = 31.1035 g — gold, silver, precious metals

Grams and ounces for recipes, postage, and small parts; kilograms and pounds for body weight, luggage limits, gym plates, and shipping.

Avoirdupois ounce (weight). A fluid ounce is a volume — see the Volume section.

Formulas:

• C → F: (C × 9/5) + 32
• F → C: (F − 32) × 5/9
• C → K: C + 273.15

Celsius for science and most of the world; Fahrenheit for US weather and some appliances; Kelvin for thermodynamics and absolute zero.

1 hp ≈ 0.7457 kW.

Horsepower for cars, lawn mowers, and pumps; kilowatts for electric motors, solar panels, and grid power. Lets you compare engine specs to electrical ratings.

• 1 PSI ≈ 6894.76 Pa
• 1 bar = 100,000 Pa ≈ 14.5 PSI

PSI for tires and US gauges; Pascals for SI and scientific; bar for European specs and compressors.

Same value, different notation. Range 1–3999. Symbols: I(1), V(5), X(10), L(50), C(100), D(500), M(1000).

Roman numerals for clock faces, outlines, copyright years, and classic numbering; convert to Arabic for arithmetic and modern use.