Concrete Stairs Calculator — m, m³, bags, cost
How to use this calculator
Pick the stair shape (straight, L-shaped, or U-shaped), then enter total floor-to-floor rise, stair width, riser height, tread depth, and waist slab thickness. Choose the unit (m, cm, or mm) from the dropdown next to each input. The calculator equalizes the risers, reports total run, slope length and stair angle, checks the Eurocode limits and the 2R+G comfort rule, and converts to m³, 25/50 kg bags, weight and cost. Tap a dimension on the diagram to jump to its input.
Cost — pick ready-mix per m³, 50 kg bags, or 25 kg bags. Select your currency (EUR, PLN, CZK, etc.).
Reinforcement — main bars along the waist + distribution bars per EN 1992-1-1, B500B rebar.
Labor — rate per step, per m³, or a flat price. Grand total sums all active sections.
Saved Calculations
| Time | Type | Rise | Steps | Vol m³ | Cost | Rebar | Labor | Total |
|---|
How to Calculate Concrete for Stairs (Metric)
A cast-in-place flight is a sloped waist slab with triangular treads cast on top, so the take-off is more than the flat-slab length × width × thickness. This tool splits the pour into steps, waist and landings, applies your waste allowance, and outputs cubic metres, 25/50 kg bags, weight, B500B reinforcement and priced labour with a selectable currency. For surrounding flatwork pair it with the concrete volume calculator and a concrete bag calculator to true up the order.
Stair Concrete Volume Formula
Volume is the sum of three parts. Steps: each tread is a triangular prism, so step concrete = treads × ½ × riser × going × width. Waist slab: waist thickness × slope length × width, where slope length = √(total rise² + total run²). Landings: on L/U flights, landing width × depth × waist thickness per landing. Number of risers = total rise ÷ target riser, rounded to a whole number; the actual riser is then back-solved so every step is equal. A 5–10% waste allowance covers form spillage and over-excavation at the base.
Code Limits and Reinforcement (EN 1992-1-1)
Eurocode national annexes typically cap the riser at 196 mm with a 254 mm minimum going and 800 mm minimum width for dwellings; comfort follows 2R + G = 600–650 mm and a 30–37° pitch. Reinforcement uses B500B steel: main bars up the waist on the tension face, distribution steel perpendicular, cover per exposure class (XC1–XC4), and 40db lap splices per EN 1992-1-1 §8.7 on 6 m bar stock. Size supporting members with the concrete beam calculator and column calculator, and detail cheek walls with the concrete wall calculator.
FAQ
How thick should the waist slab be? For dwelling flights up to a 3 m rise, 150 mm is typical (rule of thumb: slope length/20 to /25). Longer spans or commercial loading may need 200 mm or more — confirm with a structural engineer.
How much concrete for a staircase? A straight 2.7 m-rise flight, 1 m wide with 15 risers, needs roughly 0.8–1.2 m³ — about 33–50 bags of 50 kg mix. Above ~1 m³, ready-mix is cheaper and faster than bagged mix.
On pour day
Three numbers contractors most often miss on a stair pour. Minimum-load surcharge — most ready-mix plants in Europe charge €50–120 if you order under ~3 m³, so a typical 2.7 m-rise dwelling flight (0.8–1.2 m³) almost always carries the fee; price it in or combine with adjacent flatwork on the same truck. Stair formwork is the real cost driver — riser boards, side stringers and bracing typically run €25–60 per metre of stair (2025 EU), and the cast-in-place line item averages €250–600 per step all-in (formwork + concrete + rebar + finish). Strength class — exterior stoops and porches in freeze-thaw climates need C30/37 with the right XF exposure per EN 206 and Eurocode 2 cover Table 4.4N; specifying it after the truck is on site means a reschedule. Save runs to History and export the take-off as text, CSV, A4 JPG, or PDF.
