How the volume is worked out
Looked at from the side, solid steps are a row of columns. The first column is one riser tall, the second is two risers tall, and so on up to the top step or landing, which is as tall as all the risers together.
Worked example
Three steps, 7 in risers, 11 in treads, 4 ft wide, no landing. The columns are 7, 14 and 21 in tall and each 11 in deep: (7 + 14 + 21) × 11 × 48 = 22,176 in³, which is 12.8 ft³ or 0.48 yd³. Add 10% and you need 14.1 ft³ — 24 bags of 80 lb mix.
What the residential code allows
The International Residential Code sets these limits for stairs (R311.7):
| Rule | Limit |
|---|---|
| Riser height (R311.7.5.1) | 7¾ in maximum; risers in one flight within ⅜ in of each other |
| Tread depth (R311.7.5.2) | 10 in minimum; treads within ⅜ in of each other |
| Nosing | ¾–1¼ in, not required when treads are at least 11 in |
| Width | 36 in minimum |
Your local code is the one that counts
States and cities amend the IRC. Michigan, for example, allowed 8¼ in risers and 9 in treads until August 2025. Check with your building department before you set the forms.
Getting the numbers right
- Measure the total rise from where the bottom step will sit, not at the wall. Ground is graded to fall away from a house, so the rise is greater out there.
- Keep every riser the same height. A single odd step is a trip hazard, and the code only allows ⅜ in of variation.
- Wide steps with a deep landing use more concrete than you’d expect: the landing is the tallest column.
Questions people ask
How much concrete for three steps?
Three solid steps with 7 in risers and 11 in treads, 4 ft wide, take 12.8 ft³ — about half a cubic yard. With 10% extra that’s 24 bags of 80 lb mix or 32 bags of 60 lb mix.
How do I choose the riser height?
Measure the total rise from the ground to the top surface, then divide by the number of steps. Pick the number of steps that keeps each riser at or under 7¾ in — for a 30 in total rise that’s 4 steps of 7½ in, because 3 steps would need 10 in risers.
Does the landing count as a step?
Here, yes: the landing is the top step, so its height includes every riser below it. Enter its depth front to back. Leave it at 0 if the top step is the same depth as the others.
Can I fill the inside with gravel to save concrete?
If your plans allow it. The calculator assumes solid concrete all the way to the ground; if your steps will be built over compacted fill, subtract the fill’s volume from the result.
Sources for the numbers on this page
- Stairbuilders and Manufacturers Association — IRC R311.7.5.1 risers (7¾ in maximum) — 2021 IRC commentary · checked October 1, 2026
- Quikrete — Concrete Mix No. 1101 — technical data sheet (bag yields, strength gain, curing) · checked October 1, 2026
- Sakrete — Estimating bagged concrete jobs · checked October 1, 2026
- National Ready Mixed Concrete Association — CIP 8 — Discrepancies in yield (ordering 4–10% extra) · checked October 1, 2026
Corrections and updates are logged on the sources page.