To cut plasterboard, only a few tools are needed: a drywall T square and a utility / trimming knife.
Step 1 – Measure
Measure out where you need to cut your plasterboard, using your square.
You can cut the plasterboard flat, or with the sheet standing up, however the drywall T square makes cutting with the sheet standing up easier.
Step 2 – Place drywall square
The drywall square will sit on top of the plasterboard, allowing you to cut straight down the front side of the sheet against the square, giving a completely straight edge.
Step 3 – Cut board
Cut down the board towards the floor, stopping about two thirds of the way. Finish the cut upwards from the ground.
Cut through the paper and into the inner core, about a third of the way through the board. The board should then snap easily into two.
Step 4 – Finish cut
Finish the cut by scoring the back paper along the fold with your knife so the board is completely cut.
A drywall T square can also be useful when hanging plasterboard. It can be used to help line up where your studs are when screwing the plasterboard into place.