Introduction
A serial dilution is when you take a solution and dilute it step by step, making it weaker each time by the same amount. Scientists use serial dilutions every day in labs to test drugs, count bacteria, measure how strong an antibody is, and much more. Doing the math by hand for each step takes time and leaves room for mistakes.
This serial dilution calculator does all the math for you. Enter your stock concentration, pick a dilution factor, and set the number of steps. The tool instantly gives you the exact volumes to pipette at each step, a full protocol table, and a concentration decay chart. It supports common units like molarity (M, mM, µM, nM, pM), mass concentration (mg/mL, µg/mL, ng/mL), and others such as cells/mL, CFU/mL, and % w/v. For concentrations expressed in parts per million, our PPM calculator can help with conversions.
You can also use the simple dilution mode to solve a single C₁V₁ = C₂V₂ problem. For more detail on single-step dilutions, see our dedicated dilution calculator. Choose from built-in presets like 1:2, 1:10, or half-log dilution schemes, or set your own custom concentrations. The calculator shows step-by-step working with formulas so you can check every result and learn the process as you go.
How to Use Our Serial Dilution Calculator
This serial dilution calculator helps you plan dilution series and simple dilutions. Enter your stock concentration, dilution settings, and volume details. The tool will give you a full protocol table, transfer volumes, diluent volumes, step-by-step math, and a concentration chart.
Serial Dilution Tab
Presets & Quick Picks: Click a preset button to auto-fill common dilution setups. You can also click "Load Example" to see a full worked example with all fields filled in.
Dilution Scheme Preset: Pick a standard scheme like 1:2, 1:3, 1:5, 1:10, or half-log from the dropdown. Choose "Custom…" if you want to set your own fold factor and step count.
Stock Solution Name: Type a name for your stock solution, such as "Glucose" or "Antibody A." This label appears in the output protocol. This field is optional.
Diluent Name: Type the name of your diluent, such as "PBS" or "Water." This label shows up in the step-by-step instructions. This field is optional.
Stock Concentration (C₀): Enter the concentration of your undiluted stock solution. Pick the right unit from the dropdown, such as nM, µM, mg/mL, or % w/v. If you need to determine the molarity of your stock from a known mass and volume, use our molarity calculator first.
First-Step Concentration (Tube 1): Enter the target concentration for the first tube in your series. This value must be lower than or equal to your stock concentration.
Series Definition Mode: Choose how you want to define your dilution series. "Fold / Auto" uses a constant dilution factor. "Custom Concentrations" lets you type each step's concentration by hand. "Concentration Range" lets you set a start and end concentration, and the calculator finds the factor for you.
Dilution Factor per Step: In Fold mode, set how much each tube is diluted from the one before it. You can enter this as a ratio (like 1:10), a decimal factor (like 0.1), or as a transfer volume divided by a final volume.
Custom Step Concentrations: In Custom mode, type the exact target concentration for each step. Values should go from high to low down the series.
Concentration Range: In Range mode, enter a start concentration and an end concentration. The calculator works out the per-step dilution factor needed to space the steps evenly on a log scale.
Total Volume per Tube: Enter the final volume you want in each tube after mixing. Pick the unit (µL, mL, or L) from the dropdown.
Number of Steps: Enter how many dilution tubes you need. Common values are 7 for a plate column, 11 for a plate row, or 8 for general use.
Number of Replicates: Set this to 2 for duplicates, 3 for triplicates, and so on. All volumes in the output will be scaled up to match.
Include Step 0 (Stock) Row: Check this box to add an extra row at the top of the table that shows the undiluted stock.
Output Options: Use the checkboxes to show or hide the results table, step-by-step working, concentration decay chart, and final concentration indicator. You can also toggle significant figure rounding and scientific notation for very small or very large values.
Calculate / Reset: Click "Calculate" to run the calculator and see results. Click "Reset" to clear all fields and return to the default values.
Simple Dilution Tab (C₁V₁ = C₂V₂)
Stock Concentration (C₁): Enter the concentration of the stock solution you are diluting from. Choose the correct unit from the dropdown.
Target Concentration (C₂): Enter the concentration you want to end up with. This must be lower than the stock concentration.
Final Volume (V₂): Enter the total volume of diluted solution you need. The calculator will tell you how much stock to add and how much diluent to add to reach this volume.
Calculate / Reset: Click "Calculate" to get the volume of stock needed (V₁), the volume of diluent to add, the dilution factor, and a full step-by-step solution. Click "Reset" to return all fields to their defaults.
What Is Serial Dilution?
Serial dilution is a method used to lower the concentration of a solution step by step. You start with a strong solution called the stock solution. Then you take a small amount of it and mix it with a liquid called a diluent (like water or saline). This gives you a weaker solution. You then take a small amount from that weaker solution and mix it again with more diluent. Each time you repeat this, the solution gets weaker by the same amount. This repeated process is what makes it a serial dilution.
Why Serial Dilution Matters
Scientists use serial dilutions every day in labs. They are essential in biology, chemistry, microbiology, and medicine. Common uses include testing how well a drug works at different strengths, counting bacteria in a sample, preparing pH buffer series, and building standard curves for experiments. Serial dilutions are also used alongside stoichiometry calculations when preparing reagents for reactions. Without serial dilution, it would be very hard to create a wide range of concentrations quickly and accurately.
Key Terms to Know
The dilution factor tells you how much weaker each step gets. A 1:10 dilution factor means each new tube is 10 times weaker than the one before it. The stock concentration is the strength of your starting solution. If your stock is described in grams per mole, a molecular weight calculator can help you convert between mass concentration and molarity. The transfer volume is how much liquid you move from one tube to the next. The diluent volume is how much extra liquid you add to each tube to bring it to the correct final volume.
Simple Dilution vs. Serial Dilution
A simple dilution is a one-step process. You mix stock and diluent just once to reach your target concentration. It follows the formula C₁V₁ = C₂V₂, where C₁ is the stock concentration, V₁ is the volume of stock you add, C₂ is the target concentration, and V₂ is the final volume. Our dilution calculator is purpose-built for this single-step calculation. A serial dilution repeats this process across many tubes, making each tube weaker than the last. The concentration decreases following an exponential pattern, similar to how radioactive substances lose activity over time as described by half-life calculations. Serial dilutions are better when you need many different concentrations spread over a large range.
Tips for Accurate Results
Always use a clean pipette tip for each transfer to avoid contamination. Mix each tube well before taking liquid out for the next step. Very small transfer volumes (below 1 µL) can cause errors because most pipettes are not accurate at that scale. If your calculator warns you about small volumes, try increasing the total volume per tube or using a smaller dilution factor. To understand how pipetting errors propagate through your series, a percent error calculator can help you assess accuracy. When working with solutions measured in moles, double-check your unit conversions before starting the dilution to avoid compounding mistakes across every step.