CalcLibrary

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 step-by-step dilution recipe.

Examples

Three clean 1:10 molarity steps

10 mM to 10 uM with three identical 1 mL tubes.

Concentration basis
Molarity
Starting concentration
10 selected concentration unit
Stock unit
mM
Target concentration
10 selected concentration unit
Target unit
uM
Preferred per-step dilution factor
10 x
Per-step final tube volume
1 selected volume unit
Tube volume unit
mL
Total steps
3
Plan shape
3 repeated 1:10 steps
Smallest transfer volume
0.1 mL

Examples

Three clean 1:10 molarity steps10 mM to 10 uM with three identical 1 mL tubes.3
Mass concentration with an exact final landing step5 mg/mL to 0.2 mg/mL with 1:4 repeats and one custom finish.3
Fold-stock plan that triggers a tiny-transfer warning1000x to 1x with a 1:100 preference and 50 uL tubes.2

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

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

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 step-by-step 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

01What 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.
02Why 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.
03When 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.
04Does 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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