Parts Per Million (ppm) Calculation Formula

Parts per million (ppm) is used to denote concentrations in cases when the ratio of ingredient to product is very small. It is expressed as one in a million. It is equivalent to a ratio in the form of p in 1000 000 or a fraction in which the denominator is 1000 000. So, 1 ppm=1/1,000,000 or 0.0001 % of the whole.

As per USP,

PPM means parts of a gas, liquid, or solid per 1 million part of another gas, liquid, or solid containing the first gas, liquid, or solid.


1 ppm weight in volume is 1 g in 1000 000 mL.

1 ppm weight in weight is 1 mg per 1000 000 mg or 1 g per 1000 000 g. 

In volume in volume it is 1 mL in 1000 000 mL or 1 L in 1000 000 L.

PPM Calculation Examples

1. Fluoride in a water supply is expressed as parts per million w/v. Fluoride supplements should not be taken if the amount of fluoride in the water supply exceeds 0.7 parts per million w/v according to the British National Formulary (BNF). Express this ratio in mg/L.

By convention, 0.7 ppm can be represented as 0.7 g in 1000 000 mL.

Converting 0.7 g to milligrams: 700 mg

Converting 1000 000 mL into litres: 1000 L

0.7 ppm w/v = 700 mg per 1000 L = 0.7 mg/L

Therefore, it can be seen that part per million is the same as mg/L.

These representations of the concentrations of fluoride appear to be used interchangeably in documentation. In the BNF fluoride levels are expressed as ppm and micrograms/L.

2. If the concentration of fluoride is 0.25 ppm w/v, how many litres would contain 1 mg of fluoride?

0.25 ppm w/v means 0.25 g per 1000 000 mL.

Converting 0.25 g to milligrams: 250 mg

Let the amount of product in millilitres containing 1 mg of fluoride be X. 

Setting up proportional sets:

fluoride (mg) = 250 /1

product (mL) = 1000 000/X

Corresponding pairs of values are in the same ratio so:

1000 000/ 250 = X/1

Solving for the unknown in the proportional sets:

X = 1000000/250

X = 4000

Hence, 4000 mL contains 1 mg of fluoride.

Or, 4 L therefore contains 1 mg of fluoride.

3. Express 5 ppm as a percentage strength.

5 ppm = 5 part per million = 5:1000000

So, 5 part/1000000 = X parts/100 parts

X = 5 × 100/1000000 = 0.0005%

4. Convert 0.7 Milligrams Per Cubic Centimeter (mg/cm3) to Parts Per Million (ppm)

1 mg/cm3 = 1000 ppm

Thus, 0.7 mg/cm3 = 700 ppm


How do I make a 1 ppm solution?

You can prepare a 1 ppm solution by dissolving 1 mg of solute into 1000 mL of the solvent.

What is 1 ppm in grams?

1 gram in 1000000 mL.

How to make 10 ppm?

You can make a 10 ppm solution by dissolving 10 mg of solute into 1000 mL of the solvent or 10 gram solute in 1000000 mL solvent.

How to convert Milligrams Per Cubic Centimeter to Parts Per Million (mg/cm3 to ppm)?

Follow the below equation,

1 mg/cm3 = 1000 ppm

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