How much extra hardwood should I buy?

8% for straight lays, 15% diagonal, 20% herringbone.

Floating or glue-down?

Floating installs faster; glue-down sounds more solid.

About 1–1.2 kg per m² (roughly 1 gal per 40–50 sq ft).

Solid or engineered hardwood?

Engineered is more stable and works over radiant heat; solid can be refinished more.

Hardwood in the kitchen?

Yes, with a tough finish and care with water — engineered is safer.

How many times can hardwood be refinished?

Solid several times; engineered depends on the wear-layer thickness.

Hardwood flooring calculator

Floor area, layout, coverage per box and glue-down or floating: you get square footage with the waste for each pattern, boxes, and adhesive or underlayment.

Purchase quantity

290.626 ft²

Net measurement: 269.098 ft² · Waste 8 %

Boxes of hardwood15 box
Hardwood to buy290.626 ft²
Underlayment (floating)282.553 ft²

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Shopping list

What to buy for this calculation. Look up each material at your store.

Underlayment (floating) · 282.553 ft²Search at The Home Depot Search at Amazon

How it's calculated (visible formula)

area = floor × (1 + waste by layout: straight 8%, diagonal 15%, herringbone 20%); boxes = ceil(area ÷ box coverage)

Net geometric measurement, no waste.
Adjustable waste % for cuts and breakage.
Purchase rounded up to sellable units (boxes, bags, buckets, boards).

See methodology and formula versions

How to calculate it, step by step

Measure the area.
Choose the layout (straight, diagonal, herringbone) to set waste.
Work out square footage to buy.
Divide by coverage per box.
Add adhesive if glue-down or pad if floating.

Worked example: 270 sq ft straight lay, 19.4 sq ft boxes, floating

270 × 1.08 ≈ 291 sq ft
291 ÷ 19.4 = 15 boxes

→ 15 boxes and about 283 sq ft of underlayment.

Common mistakes

5% waste on herringbone.
Not acclimating wood for 48 h or more.
Gluing down over damp concrete.

Pro tips

Acclimate hardwood in the room at least 48 hours.
Leave a ⅜ in expansion gap covered by baseboard.
Test slab moisture before gluing.
Mix boards from several boxes to blend shades.

From calculation to quote

Add labor, overhead and your margin, and generate the professional PDF.

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FAQs

How much extra hardwood should I buy?: 8% for straight lays, 15% diagonal, 20% herringbone.
Floating or glue-down?: Floating installs faster; glue-down sounds more solid.
How much adhesive?: About 1–1.2 kg per m² (roughly 1 gal per 40–50 sq ft).
Solid or engineered hardwood?: Engineered is more stable and works over radiant heat; solid can be refinished more.
Hardwood in the kitchen?: Yes, with a tough finish and care with water — engineered is safer.
How many times can hardwood be refinished?: Solid several times; engineered depends on the wear-layer thickness.

Sources and standards

Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.