Cell Math / Bench Tool
Research-use calculator · responsive single-file HTML

Count.
Seed.
Passage.

Fast bench-side calculations for hemocytometer counts, dilution-corrected concentration, seeding, confluency-based passaging, and empirical growth-rate estimation. Designed for desktop and phone use.

01 / Cell Counting

From count to concentration.

For a Neubauer hemocytometer, average the count per large square, multiply by 10⁴, then correct for any sample dilution (e.g. Trypan Blue).

Count input

Live
Enter the total count across the large squares you counted. Boundary rule: include cells touching two chosen outer edges (e.g. top/left) and exclude the opposite two.
1:1 cell sample : Trypan Blue means equal volumes and a 2× dilution. Example: 10 µL cells + 10 µL Trypan Blue.
cells/mL = (n ÷ number of large squares) × 10⁴ × dilution factor
ratio dilution factor = (sample parts + diluent parts) ÷ sample parts
total cells = cells/mL × volume (mL)

Count result

Output
Average count
—
cells / large square
Dilution factor
—
× correction applied
Cell concentration
—
cells / mL
Total cells now
—
cells in current volume
Enter the cell count and current volume to calculate.
02 / Passaging

Choose the model that matches your workflow.

Count mode calculates suspension volume from cells/mL. Confluency mode uses relative occupied growth area and exponential growth.

Count-based seeding

Exact cells
Reference area and medium volume will appear here.
cell suspension per vessel (µL) = target cells ÷ concentration (cells/mL) × 1000

Seeding result

Per vessel
Cell suspension
—
µL per well / dish
Total suspension
—
µL for all vessels
Total target cells
—
cells across all vessels
Fresh medium
—
µL per vessel, if final volume is set
Enter concentration and target cells to calculate.
03 / Growth Rate

Infer growth from a real passage.

Estimate the average 24 h growth multiplier and doubling time from starting confluency, passage dilution, ending confluency, and elapsed time.

Observed growth

Back-calculate
%
Enter 10 for a 1:10 split (10× dilution; ~10% of cells retained). Enter 1 if there was no passage dilution.
%
effective starting confluency ≈ starting confluency ÷ split factor
overall growth factor = ending confluency ÷ effective starting confluency
24 h multiplier = overall growth factor^(24 ÷ elapsed hours)
doubling time = 24 × ln(2) ÷ ln(24 h multiplier)

Growth result

Average rate
Effective start after split
—
confluency-equivalent
Overall growth
—
× over the observed interval
24 h growth multiplier
—
× per 24 h
Doubling time
—
hours
Using the example values: 80% → 1:10 → 100% in 4 days.
04 / Reference

Culture-vessel area reference.

Surface areas and approximate growth-medium volumes are drawn from Thermo Fisher's “Useful Numbers for Cell Culture,” except the ibidi 8-well chamber (manufacturer-specified area). Plate/chamber areas are per well.

Important: confluency-to-cell-number relationships vary substantially by cell line, morphology, vessel coating, attachment efficiency, and handling. The confluency model is a planning estimate based on relative occupied surface area and the growth multiplier you provide; it does not assume Thermo Fisher's HeLa “cells at confluency” values.