What is a Dilution Factor?
The dilution factor (also called the dilution ratio) is a notation used to express how much of the original concentrated stock solution is present in the total solution after dilution. Knowing the dilution factor is essential in chemistry labs, medicine, food preparation, and everyday life whenever you mix a concentrated substance with a diluent (usually water).
There are two standard ways to express a dilution factor:
- S:D notation — parts of stock solution to parts of diluent (e.g., 1:9 means 1 part stock + 9 parts diluent)
- S:T notation — parts of stock solution to parts of total solution (e.g., 1:10 means 1 part stock in a 10-part total)
Dilution Factor Formula
Given Vstock (volume of stock solution) and Vdiluent (volume of diluent added):
- Vtotal = Vstock + Vdiluent
- S:D ratio = Vstock : Vdiluent (simplify by GCD) or as 1 : (Vdiluent / Vstock)
- S:T ratio = Vstock : Vtotal (simplify by GCD) or as 1 : (Vtotal / Vstock)
- Dilution factor (decimal) = Vstock / Vtotal
How to Calculate Dilution Factor — Example
Suppose you have 10 mL of acyl chloride stock solution and you add 90 mL of water.
- Vtotal = 10 + 90 = 100 mL
- S:D = 10 : 90 = 1 : 9 (simplified)
- S:T = 10 : 100 = 1 : 10 (simplified)
- Dilution factor (decimal) = 10 / 100 = 0.1
In S:D notation the dilution factor is 1:9 (1 part stock, 9 parts water). In S:T notation it is 1:10 (1 part stock in 10 total parts).
Supported Units
This calculator supports both metric and US customary (Imperial) volume units:
- Metric: µL (microliters), mL (milliliters), L (liters)
- US Imperial: fl oz (fluid ounces), cup, pint, quart (qt), gallon (gal)
You can mix units freely — for example, enter the stock volume in fl oz and the diluent in mL. The calculator converts everything to mL internally before computing the ratios.
FAQs
What is the difference between S:D and S:T notation?
S:D (stock:diluent) compares the stock volume to the diluent volume only. S:T (stock:total) compares the stock volume to the entire final volume. A 1:9 S:D ratio equals a 1:10 S:T ratio — the same dilution, two ways of expressing it.
Why does the dilution factor matter?
The dilution factor tells you how much the original concentration has been reduced. A dilution factor of 0.1 (1:10 S:T) means the final concentration is 10 times lower than the stock. This is critical when preparing chemical reagents, administering medicines, testing microorganisms, or preparing food and beverages.
Is the dilution factor the same as dilution ratio?
Yes — these terms are used interchangeably. Both express the relationship between the stock volume and either the diluent volume (S:D) or the total volume (S:T).
What is a serial dilution?
A serial dilution is a sequence of identical dilution steps applied one after another. Each step multiplies the dilution factor. For example, three consecutive 1:10 dilutions produce a total dilution factor of 1:1000 (10−3).
Can I enter volumes in different units?
Yes. You can choose independent units for the stock volume and the diluent volume. The calculator automatically converts both to mL before calculating the dilution factor.