How it works
Convert a dimensionless ratio by multiplying by the source factor and dividing by the target factor. This tool explicitly defines billion as 10⁹ and trillion as 10¹².
Input definitions
- Nonnegative ratio value
- Enter the value in the labeled unit.
- From
- Choose Fraction / Percent / Per mille / Parts per million (10⁻⁶) / Parts per billion (10⁻⁹) / Parts per trillion (10⁻¹²).
- To
- Choose Fraction / Percent / Per mille / Parts per million (10⁻⁶) / Parts per billion (10⁻⁹) / Parts per trillion (10⁻¹²).
A worked example
- Nonnegative ratio value
- 250
- From
- Parts per million (10⁻⁶)
- To
- Percent
Assumptions & limits
Dimensionless ratios only. Values above 100% are allowed for general relative comparisons. Not a conversion between mass, volume or amount-of-substance concentrations. SI writing generally prefers explicit powers of ten or quantities such as mg/kg; ppb and ppt can be ambiguous, so their powers are stated here.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-18. Content checked against the stated method and examples. Our verification approach.
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Common questions
How many ppm are in 1 percent?
One percent is 0.01 as a fraction, equal to 10,000 parts per million.
Does 1 ppm always equal 1 mg/L?
No. Ppm is a ratio and mg/L is mass per volume. Equivalence requires assumptions about density and the ratio basis; this tool does not make those assumptions.
What do ppb and ppt mean here?
Here ppb means 10⁻⁹ and ppt means 10⁻¹². These terms can be language dependent, so this tool labels their exact powers. For formal SI reporting, use explicit powers of ten or suitable ratio units.