I would divide the L into two rectangles.
For each compute rows and "columns" or tiles needed
You could use ROUNDUP to find how may rows and columns
Length of rectangle = 500; tile = 45; number of rows needed R =
ROUNDUP(500/45, 0)
Width = 400; tile = 45, number of columns C = ROUNDUP(400/45,0)
Number of tiles = R * C

But this will be approximate: suppose you need tile 45 by 10 at a wall; you
need not discard the remainder since it will give a second 45 by 10 unit.

Time to consult a DIY book? Or overpuchase at a store which will take back
unused items (my approach to carpentry every time!)
best wishes
--
Bernard V Liengme
Microsoft Excel MVP
www.stfx.ca/people/bliengme
remove caps from email

"rob" wrote in message
...
I am looking for a formula to define the number of tiles I need (full
equivalent) to put in a room with an L-shape.
I have tiles size 45 by 45 or 60 by 60 cm.
I can calculate the net size of the floor of the room, but also would like
to know how many tiles I need to order.
Any idea how excel can help me with such formula?

Rob