Stair stringer, tread, and riser calculator
Calculate the number of steps, riser height, tread depth, and stringer length for your stair project.
Stairs calculator
Choosing Stair Materials
Stair material affects safety, durability, and appearance. Building code requirements (typically 7–7.75 inch risers, 10–11 inch treads) should be your primary guide for dimensions.
Treated Lumber: The most economical choice for exterior stairs, deck stairs, and utility stairs. Pressure-treated pine resists rot and insects. Treads are typically 2x6 or 2x12 boards, and stringers are cut from 2x12 treated lumber.
Hardwood: Oak, maple, or walnut for interior stairs where appearance matters. Hardwood treads and risers provide a premium look and excellent durability. More expensive and requires finishing (stain and polyurethane).
Concrete: Poured concrete stairs are common for front entrances and commercial applications. Extremely durable and low-maintenance but expensive to form and pour. Can be finished with broom texture, exposed aggregate, or tile.
Metal Stair Stringers: Steel or aluminum stringers paired with wood, concrete, or metal treads. Metal stringers eliminate rot concerns for exterior stairs and can span longer distances than wood stringers. Often used for modern and industrial designs.
Stair Material Cheat Sheet
Use this reference to choose stair materials:
| Material | Best For | Durability |
|---|---|---|
| Treated Lumber | Exterior stairs, deck stairs, utility stairs | Moderate (needs sealing) |
| Hardwood | Interior stairs, entryways, high-end homes | High (with proper finish) |
| Concrete | Front entrances, commercial, exterior landings | Very high |
| Metal Stringers | Modern homes, exterior stairs, long spans | High (rot-proof) |
Building code requirements
- Maximum riser height: 7-3/4 inches (IRC)
- Minimum tread depth: 10 inches (IRC)
- Minimum tread width: 36 inches for main stairs
- Handrail required: 4 or more steps
- Headroom: Minimum 6 feet 8 inches
The calculator aims for riser heights close to 7 inches, which is the most comfortable and code-compliant standard for most stairs.
How to measure for stairs
Measure the total rise (vertical distance from the lower floor to the upper floor) and the total run (horizontal distance available for the staircase). Use a level and tape measure for accuracy. The total rise determines how many steps you need, while the total run determines the tread depth. Measure at multiple points along the staircase path — floors and ceilings are rarely perfectly level.
- Total rise: measure from finished floor to finished floor, not from subfloor
- Total run: measure the horizontal distance from the face of the top riser to the face of the bottom riser
- Headroom: verify at least 6 ft 8 in of clearance at every point along the stair
Stair building tips
- Build a temporary test jig with scrap wood to verify your riser and tread dimensions before cutting stringers
- Cut one stringer first and test-fit it against the actual rise and run — adjust if needed before cutting the rest
- Use 2×12 lumber for stringers; notch each tread and riser cut to at least ⅓ of the board width
- Support the bottom of the stringer on a concrete pad or pressure-treated lumber where it meets the ground
- Install handrails on both sides for stairways wider than 44 inches
Common stair projects
- Deck stairs: typically 3-6 steps, pressure-treated lumber, often with a landing pad at the bottom
- Interior stairs: 10-16 steps, finished treads (hardwood or carpet), painted or stained stringers
- Basement stairs: 8-12 steps, often steeper due to limited space, may need alternating tread design for tight openings
- Garage steps: 2-4 steps, utility-grade lumber, non-slip treads for safety
Worked example
For example, for a 8-ft total rise over 10-ft total run, with 7-in riser height:
- Steps = 8 ÷ (7 ÷ 12) = 13.7 → 14 steps
- Actual riser height = 8 ÷ 14 = 0.571 ft = 6.86 in
- Tread depth = (10 × 12) ÷ 14 = 8.57 in
- Stringer length = √(8² + 10²) = 12.81 ft
- Building code typically requires risers 4-7.75 in and treads at least 10 in
Common mistakes
| Mistake | Why it matters |
|---|---|
| Not following local building codes | Most codes require risers between 4 and 7.75 inches and treads at least 10 inches deep |
| Making inconsistent riser heights | All risers must be within ⅜ in of each other — uneven steps are a tripping hazard |
| Forgetting to account for tread thickness | The actual tread cuts on the stringer need to subtract the tread material thickness |
Frequently asked questions about stairs estimates
How do I measure a staircase?
Measure the total rise, which is the vertical height from the lower floor to the upper floor, and the total run, which is the horizontal distance the stairs will cover. Enter both into the calculator along with your desired riser height.
How many risers and treads do I need?
Divide the total rise by your target riser height and round up to get the number of steps. You will have one fewer tread than riser because the top tread is the upper floor.
How much lumber do I need for stair stringers?
Stringers are cut from 2x12 boards, typically one stringer for every 3 feet of stair width. Tread and riser material is based on your step count and stair width.
What riser and tread sizes meet building code?
Most codes require risers between 4 and 7-3/4 inches and treads at least 10 inches deep, with all steps within 3/8 inch of each other. Aim for a 7-inch riser for the most comfortable stair.