Wind Load CalculatorWind Load & Pressure Calculator
Calculate the design wind pressure and total force on fences, panels, pergolas and roofs from a basic wind speed, terrain and height. Size posts, fixings and bracing to resist real wind loads.
Why this calculation matters
Wind load decides fixing type and spacing, especially at corners and eaves where uplift is far higher than in the field of the wall.
Wind Load Calculator
Wind Load & Pressure Calculator
From local wind map. India 33-55 m/s.
Area facing the wind (fence, wall, panel).
Solid wall/fence ~1.2-1.3, pitched roof varies.
| Parameter | Value | Detail |
|---|
Assumptions. k1 (risk), k3 (topography) and k4 (cyclonic importance) are taken as 1.0, as are the Kd, Ka and Kc factors of Cl 7.2. For an ordinary structure on flat ground away from a cyclonic coast that is reasonable, but each one is a decision you should make for your own project. This is a sizing aid, not a design check.
About Wind Load Calculator
Wind exerts pressure on any exposed surface - a fence, cladding panel, pergola or roof - and that pressure becomes a force the structure and its fixings must resist. This calculator converts a basic wind speed into design pressure (accounting for terrain and height) and the total force on your surface, so you can size posts, fixings and bracing sensibly. It follows IS 875 (Part 3):2015: the design wind speed Vz = Vb k1 k2 k3 k4 (Cl 6.3), then the design pressure pz = 0.6 Vz² (Cl 7.2), with k2 read from Table 2 for your terrain category and height. Note that 0.6 is the IS 875 constant; ASCE 7 uses 0.613 and Eurocode EN 1991-1-4 uses ½ρv², so figures from those codes will not match exactly. The wind pressure calculation follows the IS 875 approach step by step, so you can show the wind load formula working in your submission notes.
Where Is This Used?
Formulas Used
Dynamic pressure q = 0.613 x V squared (V in m/s, q in Pa)Design pressure = q x Terrain factor x Height factorHeight factor = (Height / 10) ^ 0.14 (above 10m)Wind force = Design pressure x Area x Force coefficient1 kN ~ 102 kgf (divide Newtons by 9.81)How the calculation works
Wind pressure rises with the square of speed, so a modest increase in design speed is a large increase in load. The height factor matters because wind is slowed by the ground: the same storm exerts noticeably more pressure at eaves level than at ground level, and more again on open coastal terrain than in a town.
Show the formula
Design wind speed Vz = Vb x k1 x k2 x k3 x k4 (IS 875 Part 3, Cl 6.3). Design pressure pz = 0.6 x Vz^2 in pascals (Cl 7.2, where 0.6 = half the air density of 1.2 kg/m3). Force F = Cf x Ae x pz (Cl 7.3). k2 is read from Table 2 for the terrain category and interpolated linearly with height per Annex J.k1, k3 and k4 are taken as 1.0, as are Kd, Ka and Kc. In a cyclonic coastal zone k4 alone reaches 1.30, so check each factor against your own project before using this figure. The tool states these assumptions in its own output.
References and what each one provides
- IS 875 (Part 3)Bureau of Indian StandardsBasic wind speed, and the terrain, height and topography factors in Clauses 6.3 and 7.2–7.3.
Unverified values are marked as such rather than presented as sourced.
Limitations of this calculation
Derives pressure from the inputs and the IS 875 approach. It does not design the fixings that resist that pressure, and does not account for local topography, adjacent buildings, internal pressure coefficients, or dynamic response.
Do not use this for Structural design approval, cladding fixing specification, or compliance submission under any building regulation.
Figures are engineering estimates from the inputs and assumptions shown. Verify against the actual material and, where the result affects structure or safety, against a qualified professional.
- IS 875 (Part 3):2015 — Cl 6.3, Cl 7.2, Cl 7.3, Table 2
- Published worked example
Formula checked against the sources above by an automated regression test (tests/test-calculators.js) that derives each expected value independently of this page. Last reviewed .
How to use this tool
- Enter the job details below, then press Calculate.
- Pick your terrain / exposure from the dropdown.
- Fill in basic wind speed, height above ground, exposed area, force coefficient.
- Press Calculate.
Worked example
Common mistakes to avoid
- Using the basic wind speed without the terrain and height factors. IS 875 multiplies them for a reason.
- Forgetting internal pressure. Openings on the windward side add pressure from inside the building.
- Designing for pressure only. Roof edges and corners see suction that is often the worse case.
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