# Staircase Calculator

Design code-compliant stairs with this free staircase calculator. Get riser height, tread depth, stringer length, and angle.

## What this calculates

Building stairs requires precise measurements to meet building codes and ensure safety. This calculator takes the total floor-to-floor rise and computes the number of steps, exact riser height, total run, stringer length, and stair angle. It checks against IRC residential building code requirements and the comfort rule for rise-plus-run.

## Inputs

- **Total Rise** (in) — min 0, max 240 — Measure from finished floor to finished floor
- **Desired Riser Height** (in) — min 4, max 8 — IRC max: 7-3/4". Typical: 7" to 7-1/2"
- **Tread Depth** (in) — min 9, max 14 — IRC min: 10". Typical: 10" to 11"
- **Stair Width** (in) — min 24, max 60 — IRC minimum: 36". Standard: 36-42"
- **Nosing Overhang** (in) — min 0, max 1.5 — Typical: 3/4" to 1-1/4". IRC: 3/4" to 1-1/4"

## Outputs

- **Number of Risers**
- **Number of Treads** — Always one less than risers
- **Actual Riser Height** (in)
- **Total Run** (in) — Horizontal distance the stairs span
- **Stringer Length** (in) — Minimum stringer board length needed
- **Stair Angle** (°) — Comfortable range: 30-37 degrees
- **Rise + Run Sum** (in) — Comfort rule: should be 17-18 inches
- **Code Compliance** — formatted as text

## Frequently Asked Questions

**Q: What is the building code for stairs?**

A: The IRC (International Residential Code) requires: maximum riser height of 7-3/4 inches, minimum tread depth of 10 inches, minimum stair width of 36 inches, nosing between 3/4 and 1-1/4 inches, and maximum riser height variation of 3/8 inch between any two risers. Always check local codes as they may differ.

**Q: What is the ideal riser height and tread depth?**

A: The most comfortable stairs have a 7-inch riser and 11-inch tread. The comfort rule states that riser + tread should equal 17-18 inches. Steeper stairs (over 37 degrees) feel uncomfortable, while shallower stairs (under 30 degrees) waste space.

**Q: How do I calculate stringer length?**

A: Stringer length is the hypotenuse of the triangle formed by total rise and total run. Use the Pythagorean theorem: stringer = sqrt(rise² + run²). For example, with 108" rise and 120" run, the stringer is about 161.5 inches (13.5 feet). Add 12 inches to account for cuts.

**Q: Why is the number of treads one less than risers?**

A: The top landing (upper floor) serves as the final tread, so you do not need a separate tread for the last riser. For example, 14 risers require only 13 treads because the 14th step lands on the upper floor.

---

Source: https://vastcalc.com/calculators/construction/staircase
Category: Construction
Last updated: 2026-04-21