Measurement reference values
Reference values help you judge the scale of a result before you trust it. Start with the physical quantity and its unit, compare the order of magnitude, then ask whether the measurement conditions make the comparison meaningful.
Compare temperature scales and remember that phase-change values depend on pressure and composition.
Open reference →Move between millimetres, metres and kilometres while keeping powers of ten visible.
Open reference →Use familiar masses to check whether a result is in a realistic range.
Open reference →Connect laboratory volumes with cubic units and larger everyday scales.
Open reference →Compare pressure scales and keep the measurement conditions in view.
Open reference →Read energy by scale without confusing it with power or temperature.
Open reference →Interpret power as a rate of energy transfer, not an amount of energy.
Open reference →Compare processes from milliseconds to hours without losing unit consistency.
Open reference →How to use reference values
A reference value is a landmark, not a universal constant. A value can depend on temperature, pressure, composition, geometry, state of matter or the way a quantity is defined and measured.
Use these pages to estimate an order of magnitude, catch a unit-conversion error and compare an unfamiliar result with a familiar scale. They are not substitutes for experimental data when the exact conditions matter.
Order of magnitude first
If a length expected near metres appears as 0.002 m, rewrite it as 2 mm before deciding whether it makes sense. If a pressure expected near 100 kPa appears as 100 Pa, check the prefix before looking for unusual physics.
Similar numbers can describe different things
Energy and power, mass and weight, temperature and total thermal energy can produce numbers that look comparable while representing different quantities. The unit is part of the scientific statement, not decoration.