Serial Dilution Calculator

A single-step dilution to a very low target concentration would require measuring an extremely small volume of stock solution relative to the diluent, which is difficult to pipette accurately. A serial dilution breaks the total dilution into a series of smaller, more accurately measurable steps that multiply together to reach the same final concentration.

Each step divides the concentration by the dilution factor, so after n steps the concentration has been divided by the dilution factor raised to the power of n. A 10-fold dilution repeated 5 times, for example, divides the starting concentration by 10 to the 5th power -- a 100,000-fold total reduction.

For a D-fold dilution, each tube's final volume is made up of one part transferred from the previous tube (the tube's volume divided by D) and the rest diluent -- so the diluent volume is the tube's total volume minus that transfer volume. A 1:10 dilution into a 1 mL tube, for instance, uses 0.1 mL of the previous solution plus 0.9 mL of diluent.

Yes -- each transfer carries its own small pipetting error, and those errors compound across a longer series, so a 10-step series accumulates more uncertainty than a 3-step series reaching a similar final dilution with a larger fold-factor per step. Using a calibrated pipette and consistent technique matters more as the number of steps increases.

Final Concentration is rounded to 6 significant figures, not a fixed number of decimal places. A fixed-decimal-place round would silently collapse any true value smaller than roughly 5e-11 to exactly 0 -- easily reached within this calculator's declared ranges, for example 14 steps at a 10-fold dilution or 7 steps at a 100-fold dilution. Rounding to significant figures instead keeps the true magnitude visible no matter how small the final concentration gets.