What is the maximum riser height allowed by the IRC?

The maximum riser height allowed by the IRC is 7.75 inches.

What is the minimum tread depth required for stairs?

The minimum tread depth required for stairs is 10 inches according to the IRC.

Is headroom included in the stair design calculations?

No, headroom is not included in the stair design calculations, but it is an important factor to consider for safety.

Stair layout for a 66 inch rise

Calculate your stair design with a total rise of 66 inches, adhering to IRC guidelines of 7.75 inch risers and 10 inch treads. Ensure compliance and safety in your construction project.

Formula SSC-2026.1

IRC check pass

Risers / treads

9 / 8

Riser inside 4 to 7.75 in

Exact riser

7 5/16 in

186.3 mm

Total run

7 ft 0 in

2,134 mm

Stringer length

8 ft 10 13/16 in

Order 10 ft 2x12

Incline

38.16°

Square 7 5/16 in rise · 10 1/2 in run

Stringers @ 16 in

Throat 5.24 in on a 2x12

Notched 2x12 side profileLive scaled blueprint

Rise, run, and the incline are scaled from the live riser and tread. Framing-square gauges match the exact riser and the tread depth.

Bill of materials and shopping list
Item	Net	Waste	Order	Unit price	Line total	Source Spec Material / Tool
10 ft 2x12	9.51 ft cut	end cuts included	3 boards	USD	$63.00	Source Spec Material / Tool
Stringer delivery weight	84 lb	—	38 kg	2.8 lb/ft planning weight	—	Source Spec Material / Tool

Source links open a product search on the Amazon storefront for the selected currency. SiteSpecCalc may earn a commission. The link does not change the quantities above.

Side-by-side target riser
Target	Risers	Exact riser	Run	Angle	Check
7 in	9	7 5/16 in	7 ft 0 in	38.2°	Pass
7 1/2 in	9	7 5/16 in	7 ft 0 in	38.2°	Pass
7 3/4 in	9	7 5/16 in	7 ft 0 in	38.2°	Pass

Show the deterministic formula

Risers = round(total rise ÷ target rise). Exact riser = total rise ÷ risers, reported to the nearest 1/16 in and in millimeters. Treads = risers − 1. Total run = treads × tread depth.

Diagonal = hypotenuse of stringer rise and total run. A dropped header uses total rise minus landing thickness. Stock is the next 8, 10, 12, 14, 16, 18, 20, or 24 ft board.

Stringers = floor(width ÷ 16) + 1, with a minimum of 2. Throat ≈ 11.25 − (riser × tread) ÷ hypotenuse.

Contractor sign-off

Project: Stair layout for a 66 inch rise

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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.

Engineering notes

When designing stairs with a total rise of 66 inches, it is essential to adhere to the International Residential Code (IRC) guidelines, which specify a maximum riser height of 7.75 inches and a minimum tread depth of 10 inches. This ensures safety and comfort in stair use.

Note that headroom is not calculated in this design, but it is an important consideration in overall stair safety and usability.

Code reference

IRC guidelines for stair design

Field questions

What is the maximum riser height allowed by the IRC?: The maximum riser height allowed by the IRC is 7.75 inches.
What is the minimum tread depth required for stairs?: The minimum tread depth required for stairs is 10 inches according to the IRC.
Is headroom included in the stair design calculations?: No, headroom is not included in the stair design calculations, but it is an important factor to consider for safety.