With Prym's knitting calculator you get more for your money.
It is both a tool for calculating the number of stitches, but also a knitting tension template and needle gauge.
The knitting calculator helps you calculate how many stitches and rows you need in your project.
When you have a knitting sample, you can lay the calculator over it and count the number of stitches and rows you have used per 10 cm.
Then you can set the arrow to the number of stitches you have counted per 10 cm. From there, calculate the number of stitches you will need for your project.
The knitting calculator can also be used to calculate the number of rows.