Authoritative definitions of the International System of Units and SI prefixes.
Dedicated unit pair
Parts per billion to Parts per million
Convert ppb to ppm instantly, then review the formula, assumptions, and rounding guidance.
Chemistry concentration unitsInstant result
Decimals
Formula result = input × 1e-9 ÷ 0.000001. 1 ppb = 0.001 ppm
Common examples
One value, several units
Fraction0
Percent0 %
Per mille0 ‰
Parts per million0.001 ppm
Conversion table
| ppb | ppm |
|---|---|
| 1 ppb | 0.001 ppm |
| 2 ppb | 0.002 ppm |
| 5 ppb | 0.005 ppm |
| 10 ppb | 0.01 ppm |
| 25 ppb | 0.025 ppm |
| 50 ppb | 0.05 ppm |
| 100 ppb | 0.1 ppm |
Conversion chart
1 ppb0.001 ppm
5 ppb0.005 ppm
10 ppb0.01 ppm
25 ppb0.025 ppm
50 ppb0.05 ppm
Worked example
1% equals 10,000 ppm.
Unit definition
Parts per billion (ppb) One parts per billion equals 0.000000001 fraction.
Unit history
Parts per billion is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert ppb to fraction.
3. Convert the base value to ppm and apply your display precision.
Important
Mass/volume ppm equivalence depends on solution density.
Understand the result before using it
Parts per billion to Parts per million converts a value measured in Parts per billion (ppb) into the equivalent value in Parts per million (ppm). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = input × 1e-9 ÷ 0.000001
Assumptions
- Parts per billion and Parts per million represent the same dilute-solution parts quantity.
- The input is expressed in ppb; the output is expressed in ppm.
- Mass/volume ppm equivalence depends on solution density.
Worked example
1 ppb = 0.001 ppm. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a ppb measurement in a document that expects ppm.
- Compare a parts per billion value with a value reported in parts per million.
- Check the ppb-to-ppm arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- A ppm value is not automatically a mass-per-volume value; the equivalence depends on density and how concentration is defined.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Parts per billion to Parts per million?
result = input × 1e-9 ÷ 0.000001 Using the displayed relationship, 1 ppb equals 0.001 ppm.
How many Parts per million are in one Parts per billion?
One Parts per billion is 0.001 Parts per million. The displayed digits may be rounded.
Can I reverse the ppb to ppm conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts ppm back to ppb.
Is the Parts per billion to Parts per million result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.