About the Science Constants Reference Calculator
What is the Science Constants Reference Calculator?
This reference gives the values of the most used physical constants, from the 2019 redefinition of the SI and CODATA 2018 recommended values.
Since 2019, constants such as the speed of light, Planck constant, elementary charge, Boltzmann constant and Avogadro constant are exact by definition. Enter a multiplier to scale the value.
How to use the Science Constants Reference Calculator
- Constant (sample: Speed of light in vacuum (c))
- Multiply by (optional) (sample: 1)
- Press Show Constant (results also refresh as you type). The result card shows the Value, along with Unit, Status and Value × your multiplier.
Formula used
Value × Multiplier
- Exact constants = c, h, e, k, Nₐ and quantities derived from them
- Measured constants = G, particle masses, ε₀, μ₀ – with small uncertainties
Values are shown in scientific notation with SI units.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Constant | Speed of light in vacuum (c) |
| Multiply by (optional) | 1 |
| Result | Value |
|---|---|
| Value | 2.99792458 × 10⁸ m/s |
| Unit | m/s |
| Status | Exact (defines the metre) |
| Value × your multiplier | 2.9979246 × 10⁸ m/s |
Tips for using the Science Constants Reference Calculator
- R = Nₐ × k and F = Nₐ × e, so both are now exact too.
- G is the least precisely known fundamental constant.