One stair, one order record, every step shown. The stair below has 12 treads and 13 risers, runs 36 in wide, and ends in a landing. Follow the readings to the order and you can check each line against your own stair.
How many treads and risers does this stair order need?
The order is 14 closed treads, 15 riser boards, 5 landing boards, and 5 nosing sticks. A 15 percent allowance on the piece counts, rounded up to whole pieces, then rounded up again to the supplier's selling unit, turns the checked record into the supplier order. The rest of this page shows each step so you can repeat it on your own stair.
What are the readings for this stair?
Every reading comes from the checked measurement record. The riser heights use the tallest reading, and the tread depths use the deepest one, because the stock must cover the extremes, not the average.
| Reading | Value | What it fixes |
|---|---|---|
| Tread pieces | 12 | Net tread count |
| Riser pieces | 13, the top riser meets the upper floor | Net riser count |
| Stair width | 36 in | Stock length per step and nosing total |
| Tread depth | 11.5 in, deepest measured | Stock depth check |
| Riser height | 7.25 in, tallest measured | Riser board height check |
| Landing | 36 in x 42 in | Landing boards, kept on its own line |
| Nosing | 36 linear ft, one stair width per tread | Nosing sticks |
| Planning allowance | 15 percent, straight closed flight | Allowance pieces |
| Supplier selling units | 36-in closed treads, 36-in riser boards, 8-ft nosing sticks | Order rounding |
How does the riser count check out?
Count risers first, because the riser count has a trap the tread count does not. When the flight meets the upper floor with a riser, the stair has one more riser than tread. When the flight meets the landing as a tread, the counts are equal. This stair has 12 treads and 13 risers: the top riser meets the upper floor.
Check the stock before the math. The listing for the 36-in closed tread must show a depth of at least 11.5 in, because the stock depth must cover the deepest measured tread. The riser board listing must show a height that covers the tallest measured riser, 7.25 in. If the listing fails either check, the order changes before the allowance enters the record.
How does the tread and riser math work?
Apply the allowance to the piece count, never to an area. Round up at each step; a piece count never rounds down.
Order pieces = ceiling(net pieces x (1 + allowance / 100))
- Tread pieces: 12 x 1.15 = 13.8, round up to 14. One 36-in closed tread per step.
- Riser pieces: 13 x 1.15 = 14.95, round up to 15. One 36-in riser board per riser.
How does the landing become boards?
Keep the landing on its own line. Convert its depth to tread-stock boards, round up to whole boards, and then apply the allowance to the board count.
- Boards: 42 / 11.5 = 3.65, round up to 4 boards of 36 in.
- With allowance: 4 x 1.15 = 4.6, round up to 5 pieces.
How does the nosing become sticks?
Nosing is a linear quantity: one stair width per tread. Total the widths, then convert to the listing's selling unit with the listing's own stick length.
- Net nosing: 12 x 36 in = 36 linear ft.
- Sticks: 36 / 8 = 4.5, round up to 5 sticks, which delivers 40 ft. The extra 4 ft holds as repair stock.
| Line | Value | Basis |
|---|---|---|
| Net tread pieces | 12 | Checked measurement record |
| Net riser pieces | 13 | Top riser meets the upper floor |
| Allowance | 15 percent | Straight closed flight, inside the 10 to 15 percent trade-guidance range |
| Order treads | 14 closed treads | 12 x 1.15 = 13.8, rounded up |
| Order risers | 15 riser boards | 13 x 1.15 = 14.95, rounded up |
| Order landing | 5 boards of 36 in | 42 / 11.5 = 3.65 to 4 boards; 4 x 1.15 = 4.6, rounded up |
| Order nosing | 5 sticks of 8 ft | 36 / 8 = 4.5, rounded up; 40 ft delivered |
| Species and finish | One species and finish, recorded | Batch-matched delivery; lot numbers from the packing list |
What changes on a wide stair?
The piece math holds, but the width changes the stock count per step. A 52-in-wide stair with 36-in stock treads cannot cover a step with one piece, because the stair is wider than the stock. The rule is stock pieces per step = ceiling(stair width / stock length). For this stair that is ceiling(52 / 36) = 2 pieces per step.
With 10 treads, the net count becomes 10 x 2 = 20 pieces. The allowance applies to the 20: 20 x 1.15 = 23 pieces. The same allowance figure now buys 3 extra pieces instead of 2, because the wide stair cuts more pieces per step and each step wastes more offcut. Check the risers with the same stock-length rule before the order goes in.
Does the metric version match?
Run the same stair in millimetres as an independent cross-check. The piece math must agree, or one side has a conversion error. The conversions use 1 in = 25.4 mm: 36 in = 914.4 mm, 11.5 in = 292.1 mm, 7.25 in = 184.15 mm, 42 in = 1066.8 mm.
- Tread pieces: 12 x 1.15 = 13.8, round up to 14.
- Riser pieces: 13 x 1.15 = 14.95, round up to 15.
- Landing: 1066.8 / 292.1 = 3.65, round up to 4 boards; 4 x 1.15 = 4.6, round up to 5.
- Nosing: 12 x 914.4 mm = 10,972.8 mm = 10.97 m. Sticks of 2.4 m: 10.97 / 2.4 = 4.57, round up to 5 sticks, which delivers 12 m.
The metric order matches the imperial order line for line: 14 treads, 15 riser boards, 5 landing boards, 5 nosing sticks.
Which cross-checks catch the common errors?
Run at least one cross-check before the order goes in. Each check below targets one error that changes the count.
| Check | Arithmetic | Error it catches |
|---|---|---|
| Riser count | 13 = 12 + 1, the top riser meets the upper floor | Ordering 12 risers and running one short |
| Allowance base | 15 percent applied to piece counts, 12 and 13 | Applying the allowance to an area total and rounding twice |
| Rounding direction | 13.8 to 14, 14.95 to 15, 4.5 to 5 | Rounding down a piece count or a stick count |
| Stock depth | 11.5 in stock covers 11.5 in measured | Buying treads shallower than the deepest step |
| Stock length | ceiling(36 / 36) = 1 piece per step | Assuming one stock piece covers a stair wider than the stock |
| Nosing total | 12 x 36 in = 36 ft; 36 / 8 = 4.5 to 5 sticks | Ordering nosing by the foot instead of by the stick |
| Order above net | Order 14 treads against net 12, 15 risers against net 13 | Skipping the allowance or rounding down at the selling unit |
Safety and professional scope
This example covers material quantities only. It does not design the stair: stringer layout, structural tread support, fastening, rise and run, handrails, and headroom follow the project drawings, the applicable building code, and the responsible qualified person. Stair work happens at height and around open wells; keep the work area guarded and the material staged where it cannot fall or trip the crew.
Sources and scope
- National Wood Flooring Association, Installation Guidelines (© 2025): stair tread, riser, and nosing definitions; accessed 2026-10-22.
- NIST Handbook 44, 2026 Appendix C: inch to millimetre conversion; accessed 2026-10-22.
- L.J. Smith stair tread listing and Select Millwork treads pricing: pre-cut treads sold per piece in fixed lengths and depths, with return variants as separate SKUs; listings viewed 2026-10-22.
- Trade how-to pages (engineerfix.com, engineerhardwoodflooring.com, coohom.com): stair waste planning ranges of 10 to 20%; pages viewed 2026-10-22 as intent and context evidence only.
Scope: this article works one stair order end to end, with a wide-stair variant and a metric cross-check. The governing drawings, product listings, supplier return policies, applicable building code, and responsible qualified person control the accepted allowance, the final order, and the stair construction itself.
Review responsibility: Saleem Sial owns the published calculation, source, and editorial checks. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
Next, take your own readings with the stair measurement guide, choose the material with the material choice guide, run the general order method in the ordering guide, check the twelve errors in the mistakes guide, or return to the Flooring Calculators hub.
