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Serial Dilution Calculator

Plan a repeated dilution series tube by tube. Enter the stock, target, preferred step factor, and per-tube final volume to get an exact bench-ready recipe.

How It Works

Formula

R=CstockCtargetR = \frac{C_{stock}}{C_{target}}

Vtransfer=VfinalFV_{transfer} = \frac{V_{final}}{F}

Vdiluent=Vfinal−VtransferV_{diluent} = V_{final} - V_{transfer}

C1V1=C2V2C_1V_1 = C_2V_2

Variables, symbols and units

CstockC_{stock}

starting stock concentration

CtargetC_{target}

target concentration

RR

overall stock-to-target dilution ratio

VtransferV_{transfer}

volume transferred from the previous solution

VdiluentV_{diluent}

volume of diluent added to the tube

VfinalV_{final}

final volume inside the prepared tube

FF

chosen repeated dilution factor
Calculation method explained

This page plans repeated dilution steps, not a one-off C1V1 = C2V2 answer. Start with one concentration basis, enter the stock and target, choose the per-step factor you would like to repeat, and choose the final volume for each tube. The result is a bench-oriented recipe showing each tube, what concentration goes in, what concentration comes out, how much to transfer, and how much diluent to add.

First the calculator normalizes the concentrations inside the chosen basis only. The overall ratio is R = C_stock / C_target. For each repeated full step, it uses V_transfer = V_final / F and V_diluent = V_final - V_transfer, where F is the chosen per-step dilution factor.

If the requested ratio is not an exact power of F, the calculator keeps the whole repeated steps that still fit, then solves one final custom step with C1V1 = C2V2 so the last tube lands exactly on the target concentration.

Frequently Asked Questions

What does “per-step final tube volume” mean here?
It is the final volume inside each prepared tube after you add the transferred sample and the diluent. The recipe uses that same final volume for each repeated step unless the plan ends in one custom step.
Why can the last step be different from the repeated steps?
Because the overall stock-to-target ratio is not always an exact power of your preferred step factor. The planner keeps the clean repeated steps that do fit, then solves one exact final step with `C1V1 = C2V2` so the target is reached precisely.
When should I change the step factor or tube volume?
If the recipe asks for a very small transfer, the arithmetic still works, but the plan may be awkward to pipette. A smaller factor or a larger per-step tube volume usually gives a more comfortable transfer volume.
Does this validate the assay or protocol?
No. This calculator plans arithmetic dilution steps only. It does not validate sterility, calibration, pipette accuracy, recovery, adsorption, matrix effects, or protocol-specific handling.

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