ppm · mg/L · percent

Concentration converter: ppm to mg/L, ppb, and percent

Check the impurity limit in the unit your spec actually uses.

Last updated 2026-09-27. Math runs in your browser, no data leaves your computer.

Weight units like ppm and percent w/w convert among themselves by powers of ten. The moment one side is per liter, the density of the solution comes into it, which is why the SG field sits under the value.

Type the figure from the certificate of analysis or the spec sheet, with the unit it is printed in.

A COA that prints plain ppm for a liquid usually means weight per weight, so pick ppm by weight unless the lab says otherwise.

Leave 1.000 only for dilute solutions in water. For acids, caustic, brines, and solvents take the figure from SDS Section 9, because ppm and mg/L drift apart by exactly that ratio.

Before the booking, screen the name on the invoice. Shipment pre-check is on the paid plans, from USD 59 a month.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

Why ppm and mg/L are not always the same

ppm by weight counts milligrams of the substance in every kilogram of solution, and ppb counts micrograms per kilogram. Percent w/w is the same idea per hundred, so 1 percent equals 10,000 ppm and 1 ppm equals 1,000 ppb, whatever the liquid.

mg/L counts milligrams in every liter, and a liter of solution weighs SG kilograms. That gives mg/L = ppm × SG, and g/L = percent w/w × SG × 10, with percent w/v equal to g/L divided by 10. For drinking water, rinse water, and most effluent samples the SG is 1.000 to three decimals, so the two readings match and the habit of treating ppm and mg/L as the same number does no harm.

The habit breaks on concentrated product. An impurity spec in mg/L on a strong acid or a caustic solution is a stricter limit than the same figure in ppm, because every liter carries more than a kilogram of liquid. The tool makes that visible by carrying the SG through every per liter row.

Worked example: iron in hydrochloric acid

The booking. Your plant buys hydrochloric acid 32% with an iron limit of 10 mg/L, and the supplier's COA reports iron at 9 ppm. Everyone on the call treats ppm and mg/L as the same unit, so 9 sits under 10 and the lot is released for shipment, which looks fine on paper.

The failure. The acid is not water, and it weighs more per liter. At the SG of 1.16 the Sourzi density calculator carries for this grade, 9 ppm is 9 × 1.16 = 10.44 mg/L, and your incoming QC reports the lot over limit. The options are the ones you always get: take the lot on a deviation, or send it back.

The fix. Convert the limit into the supplier's unit before the purchase order goes out. At SG 1.16, 10 mg/L is 10 / 1.16 = 8.6 ppm, so the order states iron at 8.6 ppm maximum by weight, the supplier tests to the right number, and the next lot ships inside your spec.

Mixing a working solution from that concentrate? The dilution calculator handles C1V1 = C2V2 and label ratios such as 1:10 at /tools/chemicals/dilution-calculator.

If the SDS gives density in lb/gal, kg/m³, or Baumé rather than SG, the specific gravity converter produces the figure this tool needs at /tools/chemicals/specific-gravity-converter.

Frequently asked

Is ppm the same as mg/L?

Only when the solution weighs 1 kg per liter, which in practice means a dilute solution in water with an SG close to 1.000. ppm by weight is milligrams per kilogram, while mg/L is milligrams per liter, and the two differ by the density of the liquid. In a solution at SG 1.16, 10 ppm is 10 × 1.16 = 11.6 mg/L.

How do I convert percent to ppm?

Multiply the percent by 10,000, because 1 percent is one part in 100 and 1 ppm is one part in 1,000,000. So 0.5 percent w/w is 5,000 ppm and 0.002 percent is 20 ppm. This holds on a weight basis for any liquid; the density only enters when you cross over to a per liter unit such as mg/L or g/L.

What does w/w and w/v mean on a certificate of analysis?

w/w is weight of the substance per weight of solution, so 32 percent w/w is 32 g in every 100 g. w/v is weight per volume, so 32 percent w/v is 32 g in every 100 mL. For any liquid heavier than water the two figures differ, and the tool converts between them with the specific gravity of the solution.

Which SG should I enter?

The SG of the whole solution, not of the pure substance, taken from Section 9 of the SDS or from the certificate of analysis for the lot. For trace impurities in a product, that is the SG of the product itself. For a water sample or dilute rinse, 1.000 is close enough and the tool leaves it there by default.

Need a factory for this chemical?

Tell us the chemical, grade and quantity. A person on our team in Shanghai sends you a real, checked factory, and your first one is free.

Get your free Factory Match Or talk to our team

Related tools

Sourzi shows what official files say. It is not customs or legal advice. For a binding answer, ask a licensed customs broker, a CBP ruling or an Australian Border Force Tariff Advice.

File dates and links are on Data sources.