PPM Calculator

Convert parts per million to percent, ppb, mg per litre and more, work out a concentration from what you actually weighed out, or turn a gas reading into milligrams per cubic metre.

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Try 1500 ppm and see it in every other unit.

Created by James Caldwell

Last updated: September 30, 2026

What Is PPM (Parts Per Million)?

PPM stands for parts per million. It tells you how much of one thing sits inside a million parts of something else. One ppm is one part in 1,000,000, which is the same as one grain of salt in a kilogram of flour, or one second in about eleven and a half days.

PPM exists because percent runs out of room. If a chemical makes up 0.0003 percent of a water sample, that number is awkward to read and easy to mistype. The same figure is 3 ppm, which is far easier to compare against a limit. That is why water reports, air quality standards and food safety rules almost all use ppm rather than percent.

Because ppm is a ratio, it has no units of its own. It only becomes milligrams or litres once you say what the million parts are made of, which is where most of the confusion around ppm starts.

The PPM Formula: How to Calculate Parts Per Million

The basic formula divides the part by the whole and multiplies by a million:

C_{ppm} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6

The one thing people get wrong here is the bottom of the fraction. The solution is the solute plus the solvent, not the solvent on its own. If you dissolve 1 g of salt in 999 g of water, the solution weighs 1000 g, so the answer is 1000 ppm rather than 1001 ppm. The Solution tab above adds the two together for you.

Written for a percent instead, the same relationship is:

C_{ppm} = \text{percent} \times 10{,}000 \qquad \text{percent} = \frac{C_{ppm}}{10{,}000}

How to Convert PPM to Percent

Divide by 10,000. That is the whole conversion, because a percent is one part in a hundred and a ppm is one part in a million, and a million divided by a hundred is 10,000.

1,000 ppm divided by 10,000 is 0.1 percent
10,000 ppm divided by 10,000 is 1 percent
500 ppm divided by 10,000 is 0.05 percent

Going the other way, multiply by 10,000. A 2 percent solution is 20,000 ppm. A 0.5 percent solution is 5,000 ppm.

PPM Conversion Chart: Percent, PPB, PPT and mg/kg

Every row below is the same ratio written six ways. None of these need a density, because they are all comparing mass against mass or simply counting parts.

PPM	Percent	PPB	mg/kg	mg/L in water
1	0.0001%	1,000	1	1
10	0.001%	10,000	10	10
100	0.01%	100,000	100	100
1,000	0.1%	1,000,000	1,000	1,000
10,000	1%	10,000,000	10,000	10,000
100,000	10%	100,000,000	100,000	100,000
1,000,000	100%	1,000,000,000	1,000,000	1,000,000

The last column carries a warning. It only holds for water, and the reason is in the next section.

PPM to mg/L: Why They Are Equal in Water Only

You will see ppm and mg/L used as if they mean the same thing. For drinking water they very nearly do, and here is why.

One litre of water weighs one kilogram. A kilogram is a million milligrams. So one milligram in one litre of water is one milligram in a million milligrams, which is exactly 1 ppm. The two line up because water happens to have a density of 1 kg/L.

Change the liquid and the shortcut breaks:

In a brine with a density of 1.2 kg/L, a litre weighs 1.2 kg, so 1 mg/L works out as about 0.83 ppm.
In a light solvent at 0.79 kg/L, the same 1 mg/L comes to about 1.27 ppm.
In seawater at roughly 1.025 kg/L, the gap is small but real, near 0.98 ppm.

This is why the calculator above asks for a density instead of assuming one. Leave it at 1 and you get the familiar water shortcut. Change it and you get the honest answer.

Two conversions never need a density at all. A ppm is exactly the same number as mg/kg and exactly the same as micrograms per gram, because both compare mass against mass. Soil and food results are usually reported in mg/kg for precisely this reason.

How to Calculate PPM From Mass, Volume or Moles

There are four ways to arrive at a ppm figure, and the Solution tab above covers all of them. Which one you use depends on what you actually measured.

Mass in mass

You weighed the solute and you weighed the solvent. This is the cleanest method, because no density is involved anywhere.

C_{ppm} = 10^6 \times \frac{m_{solute}}{m_{solute} + m_{solvent}}

Worked example: 25 mg of a compound stirred into 500 g of water. The solution weighs 500.025 g, so the answer is 25 divided by 500,025 milligrams, times a million, which comes to 49.998 ppm. Rounding the solution to 500 g flat would have given exactly 50 ppm, and for most purposes that difference does not matter.

Mass in volume

You weighed the solute and made it up to a mark in a flask. This is the everyday laboratory case.

C_{ppm} = \frac{m_{solute}\,(mg)}{V\,(L) \times \rho\,(kg/L)}

Worked example: 25 mg made up to 500 mL of water gives 25 divided by 0.5, which is 50 ppm.

Volume in volume

Two liquids mixed by volume, or a gas blended into air. Common for solvents and for calibration gas mixtures.

C_{ppm} = 10^6 \times \frac{V_{solute}}{V_{solution}}

Worked example: 2 mL of a solvent in 1 L of mixture is 2,000 ppm. One microlitre in a litre is exactly 1 ppm.

Mole in mole

Counted by particles rather than weighed. This gives a mole fraction, which is what chemists usually want when a reaction is involved.

C_{ppm} = 10^6 \times \frac{n_{solute}}{n_{solute} + n_{solvent}}

A useful reference point: one litre of water is about 55.5 moles, so 0.001 mol of something dissolved in it works out near 18 ppm by mole fraction.

Converting PPM to mg/m3 for Gases

Air is the one place where the water shortcut fails completely, and where most people go wrong.

A ppm of gas is a volume ratio, not a mass ratio. One ppm of carbon monoxide means one microlitre of gas in every litre of air. Turning that into a mass depends on how heavy the molecules are and how much space a mole of gas takes up:

C_{mg/m^3} = \frac{C_{ppm} \times M}{V_m}

Here $M$ is the molar mass in grams per mole and $V_m$ is the molar volume in litres per mole. At 25 degrees and one atmosphere a mole of any gas fills 24.4654 litres. At freezing point it fills only 22.414 litres, which is why the temperature matters.

At 25 degrees and one atmosphere, 1 ppm works out as:

Gas	Formula	Molar mass	1 ppm equals
Carbon monoxide	CO	28.01	1.145 mg/m³
Carbon dioxide	CO2	44.01	1.799 mg/m³
Nitric oxide	NO	30.01	1.227 mg/m³
Nitrogen dioxide	NO2	46.01	1.881 mg/m³
Sulfur dioxide	SO2	64.06	2.618 mg/m³
Ozone	O3	48.00	1.962 mg/m³

Worked example: a detector reads 35 ppm of carbon monoxide. Multiply 35 by 28.01 and divide by 24.4654, which gives 40.07 mg/m³. The Gas tab above does this for twelve common gases, or for any molar mass you type in.

Where PPM Is Used

Drinking water and aquariums: hardness, chlorine, nitrate and dissolved solids are all reported in ppm, which for water is the same number as mg/L.
Air quality and workplace safety: exposure limits for gases are set in ppm, and monitors often report mg/m³, so the two get converted constantly.
Soil and food testing: results come back in mg/kg, which is ppm exactly, with no density involved.
Hydroponics and agriculture: nutrient strength is quoted in ppm, and growers move between ppm and electrical conductivity readings.
Manufacturing and metals: trace elements and impurity limits in an alloy are specified in ppm.
Laboratory work: standards and calibration solutions are prepared to a stated ppm.

How to Use This PPM Calculator

The calculator has three tabs, each for a different question.

Convert takes one number and shows it in every other unit. Type the value, choose which unit it is already in, and press Calculate. You get percent, per mille, ppb, ppt, mg/kg and micrograms per gram, plus mg/L and mg/m³ worked out from the density you set.
Solution works out a ppm from what you actually mixed. Pick one of the four methods, enter your amounts, and choose the units beside each box.
Gas moves between ppm and mg/m³ for air. Choose a gas or type its molar mass, set the temperature and pressure, and it shows the molar volume it used.

Results stay hidden until you press Calculate, and after that they keep pace with any edit you make. Reset Calculator clears everything back to empty.

Frequently Asked Questions

What does PPM mean?

PPM means parts per million. It is a ratio showing how many parts of one substance sit in a million parts of the whole. One ppm is one millionth, or 0.0001 percent.

How do you calculate PPM?

Divide the amount of solute by the total amount of solution, then multiply by 1,000,000. The total is the solute plus the solvent, not the solvent on its own.

How many ppm is 1 percent?

10,000 ppm. To go from percent to ppm multiply by 10,000, and to go back divide by 10,000.

What is 1000 ppm in percent?

0.1 percent. Divide 1,000 by 10,000. The same figure is 1,000 mg/kg, and 1,000 mg/L in water.

Is 1 ppm the same as 1 mg/L?

In water, yes. A litre of water weighs a kilogram, which is a million milligrams, so 1 mg/L is 1 mg in a million mg. For any other liquid it depends on the density. At 1.2 kg/L, 1 mg/L is about 0.83 ppm.

Is ppm the same as mg/kg?

Yes, exactly, and no density is needed. Both compare mass against mass. A ppm is also exactly the same number as one microgram per gram, which is why soil and food reports use mg/kg.

How do you convert ppm to ppb?

Multiply by 1,000. A ppb is a thousand times smaller than a ppm, so 5 ppm is 5,000 ppb. Going to parts per trillion, multiply the ppm figure by 1,000,000.

How do you convert ppm to mg/m3?

Multiply the ppm by the gas molar mass, then divide by the molar volume. At 25 degrees and one atmosphere the molar volume is 24.4654 L/mol. For carbon monoxide, 1 ppm is 1.145 mg/m³.

What is ppm in water quality?

It is how water reports state the amount of a dissolved substance. Total dissolved solids, hardness, chlorine and nitrate are all given in ppm, which for water is the same number as mg/L. Check the figure against the limit your local authority publishes, since limits differ by country and by substance.

Why does temperature change a ppm to mg/m3 conversion?

Because a ppm of gas is a volume ratio, and gas expands when it warms. A mole fills 24.4654 litres at 25 degrees but only 22.414 litres at freezing, so the same ppm reading works out as a higher mass per cubic metre when it is cold.