How conversions are calculated
Physical units use a factor relative to a common reference unit within each category. Currency uses quotes from one accepted data snapshot. Definitions with different regional conventions are identified explicitly.
Precision and limitations
Auto mode preserves significant digits for small values; manual mode rounds to the selected decimal places. ≈ means approximate; < means below the display limit. Extreme values use × 10ⁿ. Calculations are rounded only for display.
Ambiguous historical definitions remain unavailable until their convention has been verified. We do not substitute a similarly named unit without explaining the difference.
Acceleration
Acceleration describes a change in velocity per unit time. Factors are expressed relative to metres per second squared. Standard gravity is 9.80665 m/s²; local gravity can differ.
Acceleration converterAngle
Angles are converted through radians. One full turn is 2π radians or 360 degrees. NATO, Swedish and former Soviet angular mils use different divisions and are separate units.
Angle converterArea
Area factors are expressed relative to square metres. A length conversion factor is squared for area: one square foot is 0.09290304 square metres. Land-survey units use the conventions listed for each unit.
Area converterCurrency
Currency conversion uses two quotes relative to the same base currency from one accepted snapshot. Reference quotes can differ from cash, card, bank-buying, bank-selling or settlement rates.
Currency converterData size
One byte is eight bits. Decimal prefixes use powers of 1000; binary prefixes such as KiB and MiB use powers of 1024. In this tool, one word is explicitly defined as 16 bits.
Data size converterEnergy
Energy factors are expressed relative to joules. This tool uses the thermochemical calorie (4.184 J) and the International Table British thermal unit. Energy and torque can share dimensions but describe different physical quantities.
Energy converterForce
Force factors are expressed relative to newtons. Kilogram-force and related gravitational units use standard gravity of 9.80665 m/s². Pascal square metres are equivalent to newtons, not pascals divided by square metres.
Force converterLength
Length factors are expressed relative to metres. The international foot is exactly 0.3048 m and the inch is exactly 0.0254 m. These definitions do not represent the former US survey foot.
Length converterPower
Power is energy transferred per unit time, expressed here relative to watts. Mechanical, metric, electrical and boiler horsepower have different definitions and are separate choices.
Power converterPressure
Pressure factors are expressed relative to pascals. A standard atmosphere is exactly 101325 Pa and one bar is exactly 100000 Pa. Liquid-column units use conventional reference values; actual pressure depends on density and gravity.
Pressure converterSpeed
Speed factors are expressed relative to metres per second. The knot is one nautical mile per hour. The speed-of-sound example uses 343 m/s for dry air near 20°C; actual sound speed varies with conditions.
Speed converterTime
Time factors are expressed relative to seconds. For approximate duration conversion, one year is 365.25 days and one month is one twelfth of that year. Calendar months and date intervals can have different lengths.
Time converterTorque
Torque factors are expressed relative to newton metres. Pound-force and kilogram-force terms use their conventional force definitions. Torque is a rotational moment, not a substitute label for energy.
Torque converterVolume
Volume factors are expressed relative to litres. US liquid, US dry and imperial measures are separate choices. An unspecified cup here means the US customary cup; a UK beer barrel means 36 imperial gallons.
Volume converterMass
This category converts mass relative to kilograms. Avoirdupois and troy measures have different definitions. The kilonewton mass equivalent assumes standard gravity of 9.80665 m/s²; a force is not intrinsically a mass.
Mass converter