The last row of flooring is the one that ruins a job — a 20 mm sliver against the wall that no one can fit and everyone can see. This works out the row widths first, tells you to rip the first row instead, and gives you the stagger and the boxes to buy.
Notes
Why you rip the first row
If the last row comes out narrower than about a third of a plank, split the difference: take the shortfall, add a full plank width, halve it, and rip the first row to that. Both edge rows then look deliberate instead of one looking like a mistake.
Expansion gap is not optional
Wood and laminate move with humidity. The gap around the perimeter lets them, and the skirting hides it. Skip it and the floor peaks in the middle of summer.
Staggering end joints
End joints in adjacent rows should be well offset — a common rule of thumb is at least twice the plank width, never less than 150 mm. Rows that line up read as a repeating pattern and weaken the floor.
What this does not do
It lays out a rectangular room. Doorways, hearths, islands and diagonal layouts all change the count, and diagonal laying adds roughly 15 percent waste on its own.