About

Measurement conversion errors propagate through engineering calculations, manufacturing tolerances, and scientific data sets. A single misapplied factor - confusing nautical miles with statute miles, or bar with psi - has caused structural failures and mission losses (Mars Climate Orbiter, 1999). This tool converts between 100+ units across 10 measurement categories using exact SI-traceable conversion factors. All linear conversions route through a base unit per category with a multiplication factor f, while non-linear conversions (temperature) use explicit transfer functions. The tool assumes standard conditions and does not account for relativistic effects or material-specific coefficients.

Pro tip: when converting area or volume, remember the factor is squared or cubed respectively - 1 ft = 0.3048 m, but 1 ft² = 0.0929 m². Temperature is the only category here with non-linear (affine) conversion. All other categories use a pure ratio through their SI base unit.

Formulas

For all linear unit categories, the conversion from unit A to unit B is computed by routing through the SI base unit of that category:

result = value × f_Af_B

Where f_A is the factor to convert unit A to the base unit, and f_B is the factor to convert unit B to the base unit. This ensures every unit pair is reachable in O(1) without a full conversion matrix.

Temperature uses affine (non-linear) functions:

T_K = T_°C + 273.15

T_K = (T_°F − 32) × 59 + 273.15

T_°F = (T_K − 273.15) × 95 + 32

Where T_K = temperature in Kelvin (the base unit), T_°C = Celsius, T_°F = Fahrenheit. Rankine follows: T_°R = T_K × 1.8.

Reference Data

Category	Unit	Symbol	To SI Base	SI Base Unit
Length	Millimeter	mm	× 0.001	m
Length	Centimeter	cm	× 0.01	m
Length	Inch	in	× 0.0254	m
Length	Foot	ft	× 0.3048	m
Length	Yard	yd	× 0.9144	m
Length	Kilometer	km	× 1000	m
Length	Mile	mi	× 1609.344	m
Length	Nautical Mile	nmi	× 1852	m
Weight	Milligram	mg	× 0.000001	kg
Weight	Gram	g	× 0.001	kg
Weight	Ounce	oz	× 0.0283495	kg
Weight	Pound	lb	× 0.453592	kg
Weight	Stone	st	× 6.35029	kg
Weight	Metric Ton	t	× 1000	kg
Temperature	Celsius	°C	T + 273.15	K
Temperature	Fahrenheit	°F	(T − 32) × 5/9 + 273.15	K
Temperature	Kelvin	K	T	K
Area	Square Meter	m²	× 1	m²
Area	Square Foot	ft²	× 0.092903	m²
Area	Acre	ac	× 4046.86	m²
Area	Hectare	ha	× 10000	m²
Volume	Milliliter	mL	× 0.000001	m³
Volume	Liter	L	× 0.001	m³
Volume	US Gallon	gal	× 0.003785	m³
Volume	US Fluid Ounce	fl oz	× 0.0000296	m³
Speed	Meters/second	m/s	× 1	m/s
Speed	km/h	km/h	× 0.277778	m/s
Speed	Miles/hour	mph	× 0.44704	m/s
Speed	Knot	kn	× 0.514444	m/s
Data	Byte	B	× 1	B
Data	Kilobyte	KB	× 1024	B
Data	Megabyte	MB	× 1048576	B
Data	Gigabyte	GB	× 1073741824	B

Frequently Asked Questions

This tool uses the exact international inch definition: 1 in = 2.54 cm (exact, by definition since 1959). If your textbook rounds to 2.5 or 2.540, the discrepancy compounds across large values. Always verify the number of significant figures your application requires.

Temperature conversion is affine, not multiplicative. You cannot simply multiply by a ratio because the scales have different zero points. Celsius and Fahrenheit have arbitrary zeros, while Kelvin starts at absolute zero. The tool uses explicit transfer functions through Kelvin as the base, applying both a scaling factor and an offset. This is why temperature is the only category where the conversion factor field shows a formula rather than a simple multiplier.

This tool uses binary prefixes (IEC standard): 1 KB = 1024 B, 1 MB = 1048576 B. This matches how operating systems report file sizes. Hard drive manufacturers use decimal (SI) prefixes where 1 KB = 1000 B. The difference reaches 7.4% at the gigabyte scale.

Results are computed using IEEE 754 double-precision floating point (approximately 15 - 17 significant decimal digits). The display rounds to 10 significant figures by default and strips trailing zeros. For most engineering and scientific work this is more than sufficient. Be aware that very large or very small values (beyond 10¹⁵) may show floating-point artifacts.

Yes. The Volume category includes both US Gallon (3.78541 L) and Imperial Gallon (4.54609 L). Confusing the two introduces a 20% error. Similarly, US fluid ounces and Imperial fluid ounces differ. Always verify which system your recipe, specification, or regulation references.

No. Cross-category conversion requires additional physical constants or context (e.g., E = mc² for mass-energy equivalence). This tool converts within a single measurement dimension. Each category has its own SI base unit, and conversions only occur between units sharing the same dimensional analysis.