What is a dilution factor?

A dilution factor (DF) is the ratio of the final volume of a diluted solution to the volume of stock solution used, expressed as DF = V2 / V1. A dilution factor of 10 (often written 1:10) means the final solution is 10 times more dilute than the original stock, made by combining 1 part stock with 9 parts diluent to reach 10 total parts.

How do I calculate the volume of diluent to add?

First find the required stock volume using C1V1 = C2V2, rearranged to V1 = (C2 x V2) / C1, where C1 is the stock concentration, C2 is the target working concentration, and V2 is the final volume you want. The volume of diluent to add is then Diluent = V2 - V1. For example, to make 100 mL of a 2% solution from a 10% stock, V1 = (2 x 100) / 10 = 20 mL of stock, plus 80 mL of diluent.

What is the difference between dilution factor and dilution ratio?

The dilution factor (DF) compares the final volume to the stock volume (V2/V1), for example a DF of 5 for 1 part stock in a 5-part total. The dilution ratio is often written as stock:diluent, for example 1:4, meaning 1 part stock combined with 4 parts diluent to make 5 total parts. Both describe the same dilution, just expressed differently, so it pays to check which convention a protocol is using before you mix a solution.

Dilution Factor Calculator

This calculator works out the dilution factor, dilution ratio and diluent volume needed to take a concentrated stock solution down to a target working concentration, using the standard conservation of mass equation C1V1 = C2V2. You enter the stock (starting) concentration C1, the target (working) concentration C2, a display-only concentration unit such as percent, mol/L, mg/mL, ppm or fold concentrate, the final volume you want (V2), and its unit, millilitres, litres or microlitres. It returns four results: the dilution factor, how many times more concentrated the stock is than the working solution; the dilution ratio, expressed as stock to diluent; the stock volume (V1) to measure out; and the diluent volume to add to reach your final volume, alongside a working panel that spells out the mixing instructions in plain language, for example "take 20 mL of stock and add 80 mL of diluent." It suits laboratory reagent and serial dilutions, diluting concentrated cleaning chemicals or disinfectants to label strength, and mixing concentrates such as cordial or fertiliser to working strength. C1 and C2 must be entered in the same unit, and V1 and V2 in the same volume unit, since the calculator does not convert between units for you, so treat the figures as a standard dilution estimate and confirm final concentrations against your own protocol for critical laboratory or pharmaceutical work.

Method verified Standard C1V1 = C2V2 dilution equation.

1. Stock and Target Concentration

Stock (starting) concentration, C1 (any consistent unit, e.g. %, mol/L, mg/mL)

Target (working) concentration, C2 (same unit as C1)

Concentration unit label (display only)

2. Final Volume Required

Final (total) volume needed, V2

Volume unit

Your Dilution

Dilution Factor
5x
V2 / V1

Dilution Ratio

1 : 4

Stock : Diluent

Stock Volume (V1)

20 mL

Volume of stock to use

Diluent Volume

80 mL

Volume of diluent to add

Working

Stock concentration (C1)10 %

Target concentration (C2)2 %

Final volume (V2)100 mL

FormulaV1 = (C2 × V2) / C1

Stock volume required (V1)20 mL

Mixing Instructions

Take stock solution20 mL of 10 % stock

Add diluent80 mL of diluent

Total final volume100 mL

Dilution factor5x (1 : 4)

Summary: Enter your concentrations and final volume above.

How the Dilution Factor Is Calculated

Diluting a solution means adding a solvent (the diluent, usually water) to a concentrated stock solution to reduce its concentration while the total amount of solute stays the same. This relationship is described by the conservation of mass equation C1V1 = C2V2, where C1 and V1 are the concentration and volume of the stock solution, and C2 and V2 are the concentration and volume of the final, more dilute solution.

Rearranged to find the stock volume needed: V1 = (C2 × V2) / C1. The volume of diluent to add is simply the final volume minus the stock volume: Diluent = V2 - V1.

Dilution Factor vs Dilution Ratio

The dilution factor (DF) is the ratio of the final volume to the stock volume, DF = V2 / V1, or equivalently DF = C1 / C2. A dilution factor of 5 means the solution has been diluted five-fold, so 1 part stock is combined with 4 parts diluent to make 5 total parts. This is often written as a dilution ratio of 1:4 (stock:diluent) or 1:5 (stock:total), so it is worth checking which convention a label or protocol uses.

Dilution Factor	Ratio (Stock:Diluent)	Ratio (Stock:Total)
2	1:1	1:2
5	1:4	1:5
10	1:9	1:10
100	1:99	1:100

Common Uses

Laboratory reagent and serial dilutions for assays and cultures
Diluting concentrated cleaning chemicals or disinfectants to label strength
Mixing concentrated cordial, chemical concentrates, or fertiliser to working strength
Preparing standard solutions from a stock for calibration curves

Worked Example

To make 100 mL of a 2% working solution from a 10% stock: V1 = (2 × 100) / 10 = 20 mL of stock. Add 100 - 20 = 80 mL of diluent to reach the 100 mL final volume. This is a dilution factor of 5 (100 / 20), or a 1:4 ratio of stock to diluent.

Note: C1 and C2 must be in the same unit for the formula to work, and V1 and V2 must be in the same volume unit. This calculator assumes the concentration and volume units you enter are consistent; it does not convert between different units (for example percent to mol/L) for you.

Related Calculators

Sources: Conservation of mass dilution equation C1V1 = C2V2, standard chemistry and laboratory technique reference (used in analytical chemistry, biology and pharmacy dilution protocols).

This calculator provides a general-purpose dilution calculation. It does not account for volume changes on mixing (non-ideal mixing), which can occur with some chemical solutions. For critical laboratory or pharmaceutical work, always confirm final concentrations against your protocol.