Free Online Calculators
Step count, rise & run calculator
This staircase calculator helps you find the ideal number of steps, rise height, and run depth for any staircase. It sets the run with the stride formula 2 ร rise + run = 63 cm (about 25 inches) shows the stair angle and total run length and rates comfort with the safety and comfort rules. Local building code limits are not checked.
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Divide the total rise โ the finished floor-to-floor height โ by your target riser height and round to the nearest whole number, then divide the total rise by that number of risers to get the exact riser height. The number of treads is normally one less than the number of risers when the top step is the upper floor level.
Stair proportions are usually checked with three rules of thumb: the stride rule, 2 ร rise + run โ 63 cm (about 25 in, usually 59โ65 cm), the safety rule, run + rise โ 46 cm (about 18 in), and the comfort rule, run โ rise โ 12 cm (about 5 in). This calculator sets the run from the stride rule and checks the other two. The binding limits on riser height and tread depth come from your local building code.
The stringer length is the diagonal across the total rise and total run, so you square the total rise, square the total run, add them and take the square root. Add extra material at the top and bottom for the connection and the cut-off waste before buying the board.
Yes, there are free online stair calculators and mobile apps that work out riser height, tread depth, stringer length and headroom from your floor-to-floor height and available run. Most free tools give you the geometry and a printable cutting diagram; structural verification and code compliance still need a professional.
The 7โ11 rule means a maximum riser height of 7 inches and a minimum tread depth of 11 inches, a combination widely used for comfortable, safe stairs. Many residential codes allow slightly steeper stairs, but the 7โ11 proportion is the usual target for main staircases.
Start with the exact floor-to-floor height and the horizontal run available, then work out the riser count, riser height and tread depth, and check headroom and total length. From that geometry you can list the stringers, treads, risers, railing and fasteners and price material plus labour.
Convert the total rise to inches, divide by your intended riser height and round to a whole number of risers, then recalculate the exact riser height by dividing the total rise by that count. Include any floor finish thickness in the total rise before you calculate.
The most common mistakes are unequal riser heights, treads that are too shallow, forgetting to include the floor finish in the total rise, and too little headroom. Missing landings on long flights, no handrail and winders with a very narrow inner tread are also frequent problems.
The cost depends mainly on material, the number of steps, the layout โ straight, L-shaped or spiral โ and whether you include a railing and finished treads. Straight softwood stairs are the cheapest option; hardwood, curved runs and glass or steel railings raise the price considerably.
Getting your staircase dimensions right isn't just about aesthetics โ it's about safety and comfort every single time someone climbs or descends. The key measurements you need are the rise (the vertical height of each step) and the run (the horizontal depth of each tread). A typical comfortable rise falls between 17 cm and 18.5 cm, while a standard run sits around 27 cm to 30 cm. Miss these targets and your stairs will feel either exhausting to climb or dangerously steep to descend.
To find the number of steps, divide your total floor-to-floor height by your intended rise. For example, if you have a total height of 270 cm and plan for an 18 cm rise, you get exactly 15 steps. From there, multiply the number of treads (usually one fewer than the number of risers) by the run to get the total horizontal run length your staircase will consume in the room.
The gold standard for stair comfort is the Blondel stride formula, developed by French architect Franรงois Blondel in the 17th century. The formula is simple: 2 ร rise + run โ 63 cm. This figure mirrors the average human stride length, ensuring each step feels natural rather than forced. The usual range is 59 cm to 65 cm.
Let's run a quick example. With a rise of 17.5 cm and a run of 28 cm, the formula gives you: (2 ร 17.5) + 28 = 63 cm โ a perfect result. This calculator works the other way round: it sets the run so that the formula gives exactly 63 cm (run = 63 โ 2 ร rise), so the stride measure alone says nothing about comfort. That is why it also applies two more rules of thumb: the safety rule, run + rise โ 46 cm, and the comfort rule, run โ rise โ 12 cm. With a 17 cm rise and a 29 cm run all three fit exactly: 63, 46 and 12 cm.
The stair angle calculator is another useful output. Most residential staircases fall between 30ยฐ and 45ยฐ. Steeper than 45ยฐ feels more like a ladder, while anything below 30ยฐ tends to eat up too much floor space. The comfort check rates rises of 16 to 18 cm (about 27ยฐ to 34ยฐ) as comfortable, up to 19 cm (37ยฐ) as still comfortable but rather steep and anything higher as too steep, with a hint to choose a smaller target rise. Below 16 cm the stairs become rather shallow, below 15 cm too shallow. Knowing your angle upfront lets you plan your layout around the available room dimensions before any material is cut.
Always measure your total rise from finished floor to finished floor โ not just the structural floor height. Flooring materials add thickness, and even a 1โ2 cm error distributed across 15 steps can throw off every single riser. Keep the rise identical on every step: a step that is higher or lower than the others is easy to trip on.
At simple-calculator.online, this stair calculator lets you input your floor height and preferred rise, then instantly returns the number of steps, the exact rise, the run (from the Blondel formula), the total run length, the stair angle and the comfort check โ all in one place. It rates comfort only and does not check local building code limits. It's ideal for homeowners planning a renovation as well as contractors who want a fast sanity check before finalizing drawings.
A comfortable rise is typically between 16 cm and 19 cm, and a run between 25 cm and 32 cm. The Blondel formula (2 ร rise + run โ 63 cm) together with the safety rule (run + rise โ 46 cm) and the comfort rule (run โ rise โ 12 cm) shows whether your combination will feel natural to walk.
Divide your total floor-to-floor height by the intended rise height. For a 270 cm height with an 18 cm rise, that gives you 15 risers and 14 treads; with a 27 cm run the stairs need 378 cm of floor length at 33.7ยฐ.
The comfort check rates stairs up to an 18 cm rise (33.7ยฐ) as comfortable, up to 19 cm (37.2ยฐ) as still comfortable but rather steep, and anything steeper as too steep; a 20 cm rise already gives 41.0ยฐ. This is a comfort rating, not a code check: which rise and run are allowed for your stairs depends on your local building code.