Underlay
To calculate the amount of underlay needed for your floor,
measure the length and
width of the room. Multiply the two numbers together - this
figure will tell you how many square metres the underlay needs
to cover.
For example: if your room is 3 metres long and 3 metres wide,
3 x 3 = 9 square metres. You will need to buy underlay to cover
9 square metres of flooring.
Never be tempted to buy less than you really need and allow
at least an extra 5% for cutting.
Flooring
To calculate the amount of laminate floor boards needed for
your floor, measure the length and width of the room. 
Multiply
the two numbers together - this figure will tell you how many
square metres the floor needs to cover.
For example: if your room is 3metres long and 3 metres wide,
3 x 3 =9 square metres. You will need to buy underlay to cover
9 square metres of flooring. Most laminate floor packs tell
you the area they cover. However if your room is an awkward
shape make sure you get extra as you must make allowances
for cutting.
Again, don't be tempted to buy less than you need and allow
at least an extra 5%-15% for cutting depending on the shape
of your room.
Laying a laminate floor