Free reef chemistry tool

Free PPM Calculator

A PPM calculator measures a solute as parts per million of the total solution. Enter mass or water-based volume amounts to calculate PPM and instantly convert the result to PPB, percent, and mg/L.

Mass or volume basisPPM and PPBPercent conversionWater-based mg/L

Concentration calculator

Find PPM from solute and solution amounts

Solution measured by
Volume mode uses the aquarium convention that 1 mg/L is approximately 1 PPM in dilute water. For concentrated liquids or non-water solvents, use measured solution mass or account for density.

PPM result

0.5 PPM

PPB

500

Percent

5.0000e-5%

mg/L

0.5

Formula and steps

PPM ≈ solute mass (mg) ÷ solution volume (L)

  1. 1.Convert the solute to 10 mg.
  2. 2.Convert the solution volume to 20 L.
  3. 3.Divide 10 mg by 20 L to get 0.5 mg/L.
  4. 4.For dilute water-based solutions, 1 mg/L is approximately 1 PPM.

PPM

0.5

PPB

500

Percent

5.0000e-5%

mg/L in water

0.5

PPM formulas

By mass, PPM equals solute mass divided by total solution mass, multiplied by 1,000,000. For dilute aquarium water, milligrams of solute per liter of solution is approximately the same numeric value as PPM.

PPM = solute ÷ solution × 1,000,000

Aquarium measurement caution

PPM may describe different ions, compounds, or test conventions. A calcium reading and a nitrate reading cannot be compared just because both use PPM. Always match the calculation to the test kit, product label, and aquarium-safe range.

How to calculate PPM

  1. Step 1

    Choose mass or volume

    Select whether the total solution is measured by mass or by liquid volume.

  2. Step 2

    Enter the solute

    Add the amount of dissolved material and choose its mass unit.

  3. Step 3

    Enter the solution

    Add the total solution amount and its matching mass or volume unit.

  4. Step 4

    Review the result

    Read the PPM, PPB, percent, mg/L estimate, formula, and conversion steps.

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PPM calculator FAQ

What is a PPM calculator?

A PPM calculator expresses a small amount of solute as parts per million parts of the total solution. One PPM means one part of solute per 1,000,000 parts of solution.

Is 1 PPM the same as 1 mg/L?

In dilute water-based solutions, 1 PPM is approximately 1 mg/L because one liter of water has a mass close to one kilogram. The equivalence changes when solution density differs significantly from water.

How do I calculate PPM from mass?

Divide the solute mass by the total solution mass, then multiply by 1,000,000. Use the same mass unit for both amounts before dividing.

How do I convert PPM to percent and PPB?

Divide PPM by 10,000 to get percent. Multiply PPM by 1,000 to get parts per billion, or PPB.

Can I use PPM results for reef aquarium dosing?

Use PPM calculations to interpret or prepare water-based solutions only after confirming the test method, product strength, units, and safe dosing guidance. Test aquarium water before and after any dose.

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