PPM Dilution Calculator
Enter the stock concentration, target concentration, and final volume to find the stock volume and diluent volume for a ppm dilution.
Stock solution to use0.1 L
- Diluent to add
- 0.9 L
- Dilution factor
- 1:10
- Mixing instruction
- Combine 0.1 L of stock solution with 0.9 L of diluent to make 1 L at 100 ppm.
Assumes stock and target concentrations use the same ppm basis.
Assumes volumes are additive and the diluent contributes none of the solute unless noted.
How to use this calculator
- Enter the concentration of the stock solution in ppm.
- Enter the target ppm needed in the finished solution.
- Enter the final volume you want to prepare.
- Choose the volume unit you are measuring with, then read the stock and diluent volumes.
How the dilution is calculated
This calculator uses the standard dilution relationship C1 * V1 = C2 * V2. C1 is the stock concentration, V1 is the stock volume to measure, C2 is the target concentration, and V2 is the final volume after mixing. Rearranged for the unknown stock volume, the formula is V1 = (C2 * V2) / C1.
After the stock volume is found, the diluent volume is the remainder of the final mixture: Vd = V2 - V1. If the stock is 1,000 ppm, the target is 100 ppm, and the final volume is 1 L, the stock volume is (100 * 1) / 1000, or 0.1 L. The diluent is 0.9 L, so the result is a 1:10 dilution.
What changes the answer
The ratio between the stock and target concentrations drives the stock volume. A target that is one tenth of the stock concentration uses one tenth of the final volume as stock. A target that is one hundredth of the stock concentration uses one hundredth of the final volume as stock. The selected volume unit does not change the ratio; it only changes the unit used to display the measured volumes.
The final volume is the total amount after stock and diluent are combined. It is not the amount of water or other diluent you add first. If you want 500 mL at the target concentration, the stock volume plus the diluent volume should equal 500 mL.
Limits and assumptions
Dilution can lower a concentration, but it cannot make a mixture stronger than the stock solution. If the target concentration is higher than the stock concentration, you need a stronger stock or a different preparation method. If the target and stock concentrations are equal, no dilution is needed: use the full final volume of stock.
A target of 0 ppm is treated as using no stock and the full final volume of diluent. That only makes sense when the diluent is truly free of the substance being diluted. The calculation also assumes that the stock and target use the same ppm basis, such as mass per mass or mass per volume.
For dilute water-based solutions, people often approximate 1 ppm as 1 mg/L. That approximation depends on density and is not a universal unit conversion. This calculator does not adjust for density, temperature, purity, reactions, non-additive volumes, or product-specific safety limits. Very small stock volumes may also be hard to measure accurately with ordinary glassware or household tools.
Worked example
Suppose you have a 1,000 ppm stock solution and want to prepare 1 L of a 100 ppm working solution. The formula gives V1 = (100 * 1) / 1000 = 0.1 L. The diluent volume is 1 - 0.1 = 0.9 L, and the dilution factor is 1:10.
To make the mixture, combine 0.1 L of stock solution with 0.9 L of diluent to make 1 L at 100 ppm. In practice, that usually means adding the stock to a suitable container and then bringing the total volume up to the final mark with diluent.
Common questions
What formula is used for a ppm dilution?
The calculator uses C1 * V1 = C2 * V2. C1 is the stock concentration, C2 is the target concentration, V2 is the final volume, and V1 is the stock volume to measure. The diluent volume is the final volume minus the stock volume.
How much stock solution should I add to water?
Use the calculated stock volume, then add enough diluent to reach the final volume. Do not add the full final volume of water after adding stock, because that would make the finished solution too large and too weak.
What is the difference between final volume and diluent volume?
Final volume is the total finished amount after stock and diluent are combined. Diluent volume is only the amount of water, solvent, or carrier added alongside the stock. The two are different unless the stock volume is zero.
Is 1 ppm always equal to 1 mg/L?
No. The common 1 ppm equals 1 mg/L shortcut is useful for dilute aqueous solutions with density close to 1 kg/L. It is not reliable for concentrated mixtures, non-water solvents, gases, or solutions where density matters.
Can this calculator be used for chlorine or hydrogen peroxide?
The dilution math is the same when the stock and target concentrations use the same ppm basis. For reactive or hazardous chemicals, still follow the manufacturer label, compatibility guidance, ventilation requirements, and protective equipment instructions.
What does a 1:10 dilution factor mean?
A 1:10 dilution means one part of the final mixture is stock solution and ten parts are the total final volume. For example, 10 mL of stock brought up to 100 mL total volume is a 1:10 dilution.