Railing Calculator — m, balusters, posts, cost
How to use this calculator
Enter total railing length in meters, choose height (900 mm standard or 1050 mm for elevated areas), select baluster size and spacing, and configure post spacing. The calculator counts balusters, posts, rail lengths, and hardware.
EN 1991-1-1 — maximum 100 mm gap between balusters. Minimum 900 mm guard height for residential, 1100 mm for public areas.
Post spacing — typically 1.8–2.4 m on center.
Saved Calculations
| Time | Length | Height | Posts | Balusters | Cost |
|---|
How to Calculate Railing Materials (Metric)
Railing takeoffs start from the total run. Posts are set at 1.5–2.4 m on centre, then each bay is filled with balusters spaced so a 100 mm sphere cannot pass the gap (EN 1991-1-1). Order top and bottom rails per metre in standard 2.4 m lengths, add one post cap per post, and allow 10–15% waste for offcuts. 90×90 mm posts with 45×90 mm rails are the residential standard; size rough stock with the lumber volume calculator.
How to use this calculator
Pick the layout (straight, L-corner, or stair run), enter the railing length in m, set guard height (900 mm residential, 1100 mm public, 1050 mm for stairs/elevated), then choose baluster size and gap. The actual gap output is the even spacing distributed per bay so no opening exceeds 100 mm. Pair it with the deck calculator for framing and the fence calculator for similar post-and-infill runs.
Formulas Used
Posts: ⌈total length / post spacing⌉ + 1 (+ corner posts for L-layouts)
Balusters per bay: ⌊(bay clear span − post width) / (baluster width + gap)⌋
Rail length: total railing length × (1 + waste), divided into 2.4 m pieces
Actual gap: (clear span − n × baluster width) / (n + 1), capped at the 100 mm limit
Building Code Reference
EN 1991-1-1: Guards required where the fall height exceeds 600 mm. Minimum 900 mm height for residential, 1100 mm for public areas. Maximum 100 mm opening. Characteristic horizontal line load 0.5–1.0 kN/m depending on occupancy.
On install day
What gets missed on the takeoff. Rail brackets and connectors — budget 2 brackets per rail-to-post joint, so a 6 m run with 4 posts on 1.8 m centres needs roughly 12–16 brackets at €2–5 each; timber balustrade in 2025 runs roughly €60–120/m installed in residential, more for glass or aluminium infill. Post fixing — surface-mount 90×90 mm posts on a deck need a steel post anchor plus M10 through-bolts into the rim joist; do not skew-screw into endgrain. Stair length — the rail measured along the slope is roughly 1.15× the horizontal going for a typical 175 mm rise / 250 mm tread, so order rails to the slope length, not the floor distance. Save the run to History and export the diagram for the joiner or supplier.
FAQ
What is the maximum baluster spacing? The clear gap must reject a 100 mm sphere. With 38 mm balusters a 95 mm gap gives a safe margin; 100 mm is the absolute maximum.
How far apart should posts be? 1.5–2.4 m on centre. Closer spacing stiffens the run. Where posts also carry joists or studs, coordinate with the floor joist span calculator and the stud wall calculator.
Building in feet and inches? Switch to the imperial railing calculator for ft/in dimensions and IRC R312.1 (4" sphere) compliance.
