How it is calculated
The floor area gets 7 % extra for a straight layout or 15 % for diagonal, is divided by the coverage per carton and rounded up. Underlayment gets 10 % for overlaps. Baseboard runs along the perimeter minus door openings, plus 5 % for corner cuts.
Cartons = floor area × (1 + extra) ÷ coverage per cartonBaseboard = 2 × (length + width) − doors × 3 ftExample
A 15 × 12 ft room needs 10 cartons of 20 sq ft for a straight layout, 2 rolls of 100 sq ft underlayment and 7 baseboard pieces of 8 ft.
Tips from practice
- Let cartons sit in the room for 48 hours before installing.
- Run planks along the light from the main window to hide the seams.
- Leave a 1/4–3/8 in expansion gap at the walls; the baseboard covers it.
Questions and answers
How much extra laminate should I buy?
About 5–7 % for straight layouts and 10–15 % for diagonal ones or rooms with many corners.
Do I need underlayment?
Yes, unless the planks have it attached. Over concrete, use one with a vapor barrier.
Can I return unopened cartons?
Most stores take back unopened cartons. Check the policy before you buy.
Found a mistake in a formula? Write to contact@planicalc.com