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.

Thus,

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

#### FAQS

**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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