Free · Ratio conversions

Fraction, Percent & Parts-per-Million Converter

Express the same dimensionless ratio as a decimal, percentage, per mille, ppm, ppb or parts per trillion.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Edit a calculated value to solve backwards, or lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

A decimal fraction of 0.0000025 equals 0.00025%, 0.0025 per mille, 2.5 ppm, 2,500 ppb or 2,500,000 parts per trillion.

percent = fraction × 100; ppm = fraction × 10⁶; ppb = fraction × 10⁹; parts per trillion = fraction × 10¹²

Worked example

Enter these known values and leave the other values blank.

Decimal fraction
0.0000025
Percent
0.00025 %
Per mille (parts per thousand)
0.0025 ‰
Parts per million
2.5 ppm
Parts per billion
2500 ppb
Parts per trillion
2500000 ppt

Assumptions and limitations

  • All expressions must use the same numerator and denominator basis, such as mass/mass or volume/volume. This does not convert between different concentration bases.
  • Billion and trillion use the short scale, 10⁹ and 10¹². The final field spells out parts per trillion to avoid the ambiguous abbreviation ppt, which can also mean parts per thousand.

Common questions

Can I convert ppm directly to mg/L here?

No. ppm is a ratio, while mg/L is mass per volume. A conversion between them requires the concentration basis and an appropriate density.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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