How It Works
This calculator works in 4 steps.
Enter the step factor
Type the factor used at every step.
Enter the diluent per tube
Type the pre-filled volume in each tube.
Enter the tube count
Type the number of tubes in the series.
Read retained volumes
The calculator lists the volume after mixing, after transfer out, and the discard for the last tube.
The Formula
The formula subtracts the transfer volume from the mixed volume in each tube.
V_mix = V_d + V_tV_ret = V_mix − V_t = V_dV_discard = V_t- V_d:
- Diluent per tube
- V_t:
- Transfer volume
- V_ret:
- Volume left after transfer
- V_discard:
- Volume removed from the last tube
A twofold series with 100 µL per well transfers 100 µL. Wells 1 to 7 keep 100 µL each, and well 8 holds 200 µL until 100 µL is discarded.
Conversion Table
The conversion table shows the mixed, retained, and discard volumes for 5 series designs.
| Factor | Diluent per tube | Transfer | Mixed volume | Retained volume | Last-tube discard |
|---|---|---|---|---|---|
| 2 | 100 µL | 100 µL | 200 µL | 100 µL | 100 µL |
| 10 | 900 µL | 100 µL | 1,000 µL | 900 µL | 100 µL |
| 5 | 400 µL | 100 µL | 500 µL | 400 µL | 100 µL |
| 3 | 200 µL | 100 µL | 300 µL | 200 µL | 100 µL |
| 4 | 150 µL | 50 µL | 200 µL | 150 µL | 50 µL |
What Is the Serial Dilution Retained Volume Calculator?
The Serial Dilution Retained Volume Calculator is a tool that tracks the volume left in each tube after the transfer to the next tube, including the extra volume in the last tube. Every tube except the last loses one transfer volume; the last tube keeps it unless the user discards it.
Retained volume matters when each tube feeds an assay that needs a set volume. Without a discard step, the last tube in a twofold series holds twice the volume of the other tubes. The calculator flags this unequal volume and shows the discard amount that makes all tubes equal.
Common Uses
There are 5 main uses of this calculator.
Equal well volumes
Researchers keep all wells at the same volume for optical readings.
MIC panels
CLSI broth methods discard the last transfer to keep 100 µL per well.
Downstream volume checks
Users confirm each tube holds enough volume for duplicate assays.
Waste tracking
Labs count discarded volume for hazardous drugs.
Robot method checks
Automation teams add a discard step to liquid handler programs.