Cell Seeding Calculator – Free Calculator

Understanding the cell seeding calculator — concept and principle

Seeding plates evenly is the first step of most cell-based assays. You know how many cells you want in each well and how much medium each well holds; the question is how much of your counted cell suspension to take and how much medium to add. This calculator prepares one master mix for all wells, with a small overage so you do not run short while pipetting.

2.112 mL of stock plus 8.448 mL of medium gives 20,000 cells in each 100 µL well.

How it is calculated

Cells needed = target cells per well × wells × (1 + extra %/100)
Suspension needed (mL) = cells needed ÷ suspension concentration (cells/mL)
Total mix volume (mL) = wells × volume per well (µL) ÷ 1000 × (1 + extra %/100)
Medium to add (mL) = total mix volume − suspension needed

The suspension concentration usually comes from a hemocytometer or automated count of live cells.

The principle

The calculation is a simple dilution, C₁V₁ = C₂V₂. The final concentration of the mix must equal the target cells per well divided by the volume per well. Taking V₁ of a suspension at C₁ delivers C₁V₁ cells, and topping up with medium to the total volume brings the mix to the right concentration. Preparing one mix for all wells, instead of adding cells to each well separately, keeps every well at the same density. The overage covers dead volume in reservoirs and tips.

Worked example

Inputs: suspension 1 × 10⁶ cells/mL, 2 × 10⁴ cells per well, 96 wells, 100 µL per well, 10% extra.
Cells needed = 20,000 × 96 × 1.1 = 2,112,000 cells.
Suspension needed = 2,112,000 ÷ 1,000,000 = 2.112 mL.
Total mix = 96 × 100 ÷ 1000 × 1.1 = 10.56 mL.
Medium to add = 10.56 − 2.112 = 8.448 mL.
Check: 2 × 10⁴ cells in 0.1 mL is 2 × 10⁵ cells/mL, and 2,112,000 ÷ 10.56 mL gives the same value.

Each point is the calculator re-run with only “Cell suspension (cells/mL)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Cell suspension (cells/mL)	Suspension needed (mL)
250,000	8.448
500,000	4.224
750,000	2.816
1e+06	2.112
1.25e+06	1.6896
1.5e+06	1.408
2e+06	1.056

How to read the result

If the medium to add is negative, the suspension is too dilute to reach the target in the chosen volume: concentrate the cells by centrifugation and resuspension, or lower the target. If the suspension volume is very small, such as a few microlitres, make an intermediate dilution first to pipette accurately. A 10% overage is a common choice for multichannel pipetting from a reservoir.

Common mistakes

Using the total cell count instead of the live cell count.
Letting cells settle in the tube or reservoir, which makes the last wells sparser; mix gently but often.
Entering volume per well in mL in the µL field.

Keep in mind: The calculation assumes an accurate count and a uniform suspension. Clumps, poor mixing and counting error all translate directly into uneven wells, so recount when density matters and validate seeding density for each assay.

Frequently asked questions

How do I choose the number of cells per well?

It depends on the cell type, plate format and assay length; common practice is to test a range and choose a density that stays sub-confluent until the end of the experiment.

Should the extra percentage be larger for small volumes?

Often yes. Dead volume is roughly constant, so it is a bigger fraction of a small total.

Can I seed several plates from one mix?

Yes. Enter the total number of wells across all plates, and mix the suspension between plates.

Sources: Freshney, R. I., Culture of Animal Cells: A Manual of Basic Technique and Specialized Applications (Wiley) · ATCC, Animal Cell Culture Guide

Checked 8 Nov 2026. Standard textbook formulas in SI units, computed in your browser. For learning and estimates — real designs must follow your local codes and be checked by a qualified engineer.

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