Trypan blue exclusion is the everyday way to measure how many cells you have and what fraction are alive before seeding, transfecting, or freezing. This calculator turns your haemocytometer counts into cell density and viability, and scales up to the total cells in your tube.
How it works
A haemocytometer large square holds a known volume of 0.1 µL, so density follows directly from the average count per square:
density (cells/mL) = (live + dead) / squares × dilution × 10,000
live density = live / squares × dilution × 10,000
viability % = live / (live + dead) × 100
total cells = density × suspension volume (mL)The factor of 10,000 converts the 0.0001 mL square volume to a per-millilitre basis. Viability is independent of the dilution factor because both live and dead counts scale the same way.
Example and tips
Counting 4 large squares with 720 live and 80 dead cells at a 2× trypan blue dilution gives an average of 200 cells per square, a density of 4 × 10⁶ cells/mL, and 90% viability. Keep total counts above ~100 cells for accuracy, and read the chamber within a few minutes — prolonged trypan blue exposure is itself toxic and will understate viability. Clumped cells bias counts, so ensure a single-cell suspension before loading.