Stair Calculator
Enter the floor to floor height and the going you want. The calculator picks the number of steps, shows the pitch and checks the figures against the building regulations for homes in England.
This is a planning aid only. Building control or a stair maker must confirm the final design.
Worked examples
A standard house stair
Floor to floor 2,600 mm, going 250 mm
15 risers of 173.3 mm, pitch 34.7 degrees, 2R+G 597 mm
It meets the limits, with a run of 3.5 m along the floor.
About Stair Calculator
A stair calculator turns the height between two floors into a staircase that works. A staircase has a whole number of steps, and every rise in the flight has to be the same, so the height of each step is the floor to floor height divided by the number of risers. The going is how far each step goes forward. Together they set the pitch, the steepness of the stairs.
The tool tests several numbers of steps and checks each against the figures for stairs in a home in England: a rise of 150 to 220 mm, a going of 220 to 300 mm, a pitch of no more than 42 degrees, and twice the rise plus the going between 550 and 700 mm. It picks the choice with a rise nearest to 175 mm and shows the length the flight takes along the floor.
How to use Stair Calculator
- Measure from the top of the finished floor below to the top of the finished floor above.
- Enter that height in millimetres and the going you want.
- Check the result and the table of other numbers of steps.
- Check the length of the flight fits the space available.
Common uses
- Planning a loft conversion
- Replacing an old staircase
- Building a straight flight to a garden room
- Checking a stair maker's drawing
Frequently asked questions
What are the rules for stairs in a house?
In England, Approved Document K gives a rise of 150 to 220 mm, a going of 220 to 300 mm and a maximum pitch of 42 degrees for stairs in a home. Twice the rise plus the going should be 550 to 700 mm. The tool uses the 2013 edition.
How many steps do I need for a floor to floor height of 2.6 m?
With a going of 250 mm, 15 risers of 173.3 mm give a pitch of 34.7 degrees and 2R plus G of 597 mm. That meets all the limits, and needs 14 treads and a 3.5 metre run.
Do the rules differ in Wales, Scotland and Northern Ireland?
Yes. Each has its own regulations and some limits are stricter, for example a smaller maximum rise in Scotland. Ask building control in your area.
What is the going of a stair?
It is the horizontal depth of a tread, measured from the front edge of one step to the front edge of the next, not including any nosing overhang beyond the riser.
Is a steep staircase allowed?
Only in some cases such as a loft conversion where space is limited, and rules apply. A staircase steeper than 42 degrees needs building control approval.