Parts per million (ppm) is one of chemistry’s most versatile concentration units, appearing in water-quality reports, environmental regulations, analytical calibration curves, food-science flavour profiles, and spectrophotometric assays. This calculator collects the seven most common ppm-related calculations into a single tool, each with solve-for-variable logic so you can work in any direction.
How it works
The calculator offers seven modes, selectable from the dropdown at the top:
Mass ppm (mg/kg) — the foundational definition. One ppm by mass means one milligram of solute per kilogram of solution. You can solve for the ppm value, the mass of solute you need to weigh out, or the total solution mass required to hit a target concentration. For dilute aqueous solutions the density approximation gives ppm ≈ mg/L, which is why water-quality data uses both notations interchangeably.
Volume ppm (µL/L) — used for gas standards and liquid flavourings. One µL of analyte per litre of carrier gives 1 ppm (v/v). This mode solves for ppm, solute volume, or solution volume.
PPM → Molarity — converts mg/L to mol/L using M = ppm ÷ (M_r × 1000). Enter the molar mass of your compound (e.g. 58.44 g/mol for NaCl, 180.16 for glucose) and the calculator returns the molar concentration and the equivalent in µmol/L.
Molarity → PPM — the reverse: ppm = M × M_r × 1000.
Beer-Lambert (A = ε·l·c) — probably the most-used equation in analytical chemistry. The absorbance A is proportional to the molar attenuation coefficient ε (L mol⁻¹ cm⁻¹), path length l (cm), and molar concentration c (mol/L). Solve for any one of the four quantities; the transmittance T = 10^(−A) × 100 % is shown alongside absorbance.
Dilution (C₁V₁ = C₂V₂) — conservation of moles of solute. Pipe a stock concentration and aliquot volume into a final volume to find the resulting concentration — or rearrange to find how much stock to take, what final volume to make up to, or what stock you need.
PPM / PPB / PPT converter — enter a value in ppm and instantly see the equivalent in ppb (× 10³), ppt (× 10⁶), % by mass (÷ 10⁴), and the common mg/L, µg/L, ng/L notation for aqueous samples.
Worked example — Beer-Lambert absorbance of a KMnO₄ solution
Potassium permanganate (KMnO₄) has a molar attenuation coefficient of about 2240 L mol⁻¹ cm⁻¹ at 525 nm. You prepare a 0.001 mol/L solution and measure it in a 1 cm cuvette:
A = ε · l · c = 2240 × 1 × 0.001 = 2.24
That absorbance is above the reliable Beer-Lambert range (typically A < 1), so you dilute it tenfold to 0.0001 mol/L:
A = 2240 × 1 × 0.0001 = 0.224 — now in the linear range.
Using the dilution mode with C₁ = 1000 ppm, V₁ = 10 mL, V₂ = 100 mL confirms C₂ = 100 ppm — a ten-fold dilution.
Formula reference
| Mode | Formula |
|---|---|
| Mass ppm | ppm = mass(mg) ÷ solution(kg) |
| Volume ppm | ppm = volume(µL) ÷ solution(L) |
| PPM → Molarity | M = ppm ÷ (M_r × 1000) |
| Beer-Lambert | A = ε · l · c |
| Dilution | C₁V₁ = C₂V₂ |
| Unit conversion | 1 ppm = 10³ ppb = 10⁶ ppt = 10⁻⁴ % |
All calculations run entirely in your browser — no data is uploaded or stored anywhere.