Example: an 18 × 14 ft room
The floor is 252 ft², or approximately 23.412 m². With an illustrative 10% additional trimming allowance, required coverage is 277.2 ft². At an assumed net coverage of 100 ft² per roll, 277.2 ÷ 100 = 2.772, rounded to three rolls. This assumes any seam deduction is already included in the 100 ft² figure.
Identify the complete flooring system
A product with an attached pad does not automatically have the same requirements as one without a pad. Pergo publishes installation information by flooring product, which is the right place to check permitted layers. Do not order extra underlayment just because another floor installation used it.
Keep sound-control layers, moisture-control layers and surface preparation distinct in the estimate. One product may perform several functions, but that must be established by its documentation. The quantity calculator cannot determine assembly compatibility or whether the substrate is ready for installation.
Measure rooms without losing small connecting areas
Draw each room, closet, passage and alcove that receives this same layer. Split irregular shapes into rectangles and keep their areas in a short schedule. Avoid counting a doorway zone in both adjacent rooms. A room that receives a different flooring system belongs on a different underlayment line.
Deduct permanently excluded areas only when their treatment is settled. Record the scope around fixed cabinetry and other obstructions rather than guessing from a marketing floor plan. If a measurement changes, your room schedule should show exactly which subtotal changed.
Use net coverage and a real strip layout
Roll width multiplied by roll length gives gross material area. The usable floor coverage depends on the product’s required seam treatment and any integral flap or overlap arrangement. Copy a documented net coverage where available; otherwise work out the layout from the actual roll dimensions and instructions.
Do not reduce coverage for a seam and then add a second allowance for that same seam. Keep only additional trimming and handling loss in the waste field. A narrow corridor can create different offcuts from a wide room even when their floor areas match.
Round at the point where material can be shared
Combine compatible rooms when usable roll remnants can move between them. Round the combined requirement to whole rolls after the allowance. If work is separated into delivery phases or different products, retain separate orders and accept that their rounding may create more spare material.
Confirm whether seam tape or another accessory is included with the roll. Measure those accessories on their own basis. Underlayment quantity also does not include skirting, transitions, adhesives or levelling compounds; list them separately so the floor package can be reviewed without hidden assumptions.
Do it in order
- Confirm the permitted underlayment for the exact flooring.
- Sum measured room and passage areas without overlaps.
- Enter usable coverage after the specified seam treatment.
- Add only remaining losses and round compatible work to rolls.
Planning boundary
This is a roll quantity estimate, not a moisture assessment, sound rating or approval of a flooring assembly.
Sources checked
Should underlayment match the flooring carton waste?
Not automatically. Board cutting and roll layout can have different losses, so document each separately.
Can I put another pad under attached-pad flooring?
Check the exact flooring manufacturer’s instructions. The quantity tool does not decide whether an additional layer is permitted.