Parts Per Billion Calculator

Work out parts per billion instantly with clear inputs, formula shown and shareable results.

About Parts Per Billion Calculator

Parts per billion is a mass ratio scaled by 10^9, used where a concentration is far too small to read comfortably as a percentage. Half a milligram of contaminant in a kilogram of solution is 0.5 ppm or 500 ppb, and because water is close to 1 kg per litre, ppb also reads as micrograms per litre for dilute aqueous samples.

Formulas

Parts per billion

ppb = (solute mass / solution mass) x 1,000,000,000

Relation to ppm

1 ppm = 1000 ppb

Worked example

With the default values below, Parts Per Billion Calculator returns Concentration of 500.000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Solute massminimum 0 mg: 0.5 mg
Total solution massminimum 0 kg: 1 kg

Results

Concentration: 500.000 ppb
Same Value In ppm: 0.500000
Same Value As Percent: 0.00005000%
Micrograms Per Kilogram: 500.000

Step by step

1Values used
2Parts per billion
3Relation to ppm
4Concentration= 500.000 ppb
5Same Value In ppm= 0.500000
6Same Value As Percent= 0.00005000
7Micrograms Per Kilogram= 500.000

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 8 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is ppb the same as micrograms per litre?

For dilute water samples, effectively yes, because one litre of water has a mass of about one kilogram. For other solvents you must use the actual density.

Why not just use a percentage?

A 500 ppb result would be 0.00005% - a string of leading zeros that is easy to misread. ppb keeps trace figures readable.