Here is a formula for calculating stitches and rows from a tension swatch from Jessie Dennett in Wakkerstroom, South Africa, who writes:

Dear Anne
I hope you have recovered from your surgery and are now feeling bright eyed and bushy tailed! I have a little contribution for the magazine, one that has seen me safely through many hundred knitted jerseys. It was shown to me by my Passap teacher Lena De Lima here in Johannesburg when I first bought my machine. I have never used any other method to work out the correct size of my jerseys. It is simplicity itself!

Knit a tension swatch, 40 stitches wide and 60 rows long. Leave it for a couple of hours or longer and then measure it. Find a calculator and the formula is:

What you want - the garment width or length
Multiplied by what you have - 40 sts or 60 rows
Divided by what you know - size of your swatch

This, believe it or not, will give you how many stitches or rows are required! I will give you an example to make things a bit clearer.

My tension swatch measures 40 sts / 15 cm and 60 rows / 8 cm
My jersey is 54 cm chest, 24 cm long without the rib.
54 cm x 40 sts = 2160 ÷ 15 cm 144 stitches
Divide 144 into 2 for Back and Front 72 stitches.
For length, 24 cm x 60 rows = 1440 ÷ 8 cm 180 rows.

It really is easy! Good luck with the magazine.
Jessie Dennett
Wakkerstroom, South Africa