Concrete Steps Calculator

What the concrete steps calculator does

Concrete steps are poured solid, so a small flight can swallow more concrete than you would guess. This works out how much. You give it the shape of one step and how many there are, and it returns the total volume in cubic yards and cubic metres, plus pre-mixed bag counts.

It is built for a solid set of stairs, the kind that leads up to a porch or a door. Below is how it adds the steps up, what the measurements mean, and a worked example.

How to use it

1. Enter the width. How wide the stairs are, side to side, with its unit.
2. Enter the rise and run. The rise is the height of each step, and the run is how deep each step is, front to back.
3. Enter the depth. How far the solid landing behind the top step reaches back.
4. Enter the step count, then press Calculate for the breakdown, or Reset to clear it.

How the volume is worked out

Picture a set of solid concrete stairs from the side. It is a staircase shape: the bottom step is one block, the next sits on top and behind it, and so on, so each step adds another layer of concrete. Behind the top step is a solid landing.

The calculator works exactly that way. It adds up the concrete in each step as it climbs, then adds the landing block behind them, which is its own depth and width by the full height of the flight. Everything is converted to one common unit first, then the total comes back in both cubic yards and cubic metres. There is no hollow inside, because the steps are poured solid.

Rise, run, and comfortable steps

The calculator pours whatever stairs you describe, but two of the numbers decide whether they are comfortable to walk. The rise is the height you step up each time, and the run is how far forward your foot lands. Stairs that feel right tend to sit near a 7 inch rise and an 11 inch run, and building codes cap how steep they can be, usually around a 7 and 3/4 inch maximum rise.

It is also worth keeping every step the same. The thing that trips people on stairs is one step a different height from the rest, so if the steps are anything someone will use daily, it is worth checking the rise and run against your local code before you build the forms.

Units, rounding, and how precise this is

You can enter each measurement in inches, feet, yards, millimetres, centimetres, or metres, in any mix. The result comes back in cubic yards, the way ready-mix is ordered in the US, and cubic metres for everywhere metric.

Volume is rounded to two decimal places, and the bag counts are always rounded up to a whole bag. The figure is the solid volume of the stairs as you have described them, so a little extra on the day is sensible, which the ordering section covers.

A worked example: a set of three steps

Say you are pouring three steps, 4 feet wide, each with a 7 inch rise and an 11 inch run, with the landing reaching 12 inches behind the top step.

Adding up the three solid steps and the landing block behind them comes to about 0.50 cubic yards, or 0.38 cubic metres. That is in the range of roughly 23 bags of 80 lb mix, which for a quick set of steps is borderline between bagging it and ordering a small load.

Forming and ordering

Steps are usually poured into timber forms, and sometimes over a packed base or rubble fill to save concrete on the inside of a large flight. If you fill the core, the calculator's solid figure will be more than you actually pour, which is no bad thing as a safety margin.

Either way, add about 5 to 10 percent when you order. Forms leak at the corners, and steps have plenty of corners. Running short part-way up a flight means a visible joint between pours, so it is worth having a little spare.

Questions people ask

How much concrete do I need for steps?

It depends on the size and number of steps. A solid set of three 4-foot-wide steps with a small landing comes to about half a cubic yard.

What are rise and run?

The rise is the height of each step, and the run is how deep each step is front to back. Comfortable stairs are often near a 7 inch rise and an 11 inch run.

What is a standard step height?

Around 7 inches is typical and comfortable, with building codes usually capping the rise near 7 and 3/4 inches. Keeping every step the same height matters most.

How many bags of concrete for steps?

It follows the volume. As a guide a cubic yard is about 45 bags of 80 lb mix, so a half-yard set of steps is in the region of 23 bags.

References

A quick note on where these figures come from. The unit conversions, including that one cubic yard is 0.7646 cubic metres, follow the US National Institute of Standards and Technology guide. The weight used to estimate pre-mixed bags is the standard density of normal-weight concrete, about 2,400 kg per cubic metre, tabulated in the Portland Cement Association's Design and Control of Concrete Mixtures. The comfortable and maximum rise and run figures come from stair provisions in the International Residential Code.

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (SI). https://www.nist.gov/pml/special-publication-811
2. Portland Cement Association (PCA), Design and Control of Concrete Mixtures. https://www.cement.org
3. International Code Council, International Residential Code, Section R311.7 (stairways, rise and run). https://codes.iccsafe.org