# How is hemocytometer cell count calculated?

## How is hemocytometer cell count calculated?

To calculate the cell concentration, take the average number of viable cells in the four sets of 16 squares and multiply by 10,000 to get the number of cells per milliliter. Then, multiply this by five to correct for the one in five dilution from the trypan blue addition.

### Why do you multiply by 10000 when counting cells?

You can think of each large square as having a volume of 100nL. So you have to multiply by 10,000 in order to convert the number of cells in 100nL to the number of cells per mL.

**How do you calculate viable cell count?**

The total number of colonies is referred to as the Total Viable Count (TVC). The unit of measurement is cfu/ml (or colony forming units per milliliter) and relates to the original sample. Calculation of this is a multiple of the counted number of colonies multiplied by the dilution used.

**How do you manually count cells?**

Manually Count Cells in Sample Focus both onto the grid pattern and the cell particles, and count the total number of cells found in 4 large corner squares. If cells are touching the 4 perimeter sides of a corner square, only count cells on 2 sides, either the 2 outer sides or 2 inner sides.

## What is the rule used when counting cells in a haemocytometer?

The rule is to count all the cells in the middle and those on two lines. You choose which two lines to count (bottom, upper, left or right) just try to count all the time the same lines to reduce final counting errors and deviations. The point of this “rule” is to avoid double counting.

### What is the formula for dilution factor?

How is a dilution factor determined? A dilution factor is the total volume of a sample plus diluent after dilution divided by the inital volume of sample. 100 mL of final volume รท 2 mL original volume of sample = 50 dilution factor.

**How is CFU count calculated?**

To find out the number of CFU/ ml in the original sample, the number of colony forming units on the countable plate is multiplied by 1/FDF. This takes into account all of the dilution of the original sample. For the example above, the countable plate had 200 colonies, so there were 200 CFU, and the FDF was 1/4000.