Wind Load Calculator — ASCE 7-22 Velocity Pressure and Wall Design Pressure

Background.

Put a two-storey house on open ground where the mapped design wind is 115 mph, and the 300 square feet of wall facing that wind has to be designed for about 7,300 pounds of push. At the same moment the wall on the far side is being pulled outward with about 70% of that pressure, and the side walls are being sucked outward harder still. A push on one face and suction on the others is the pattern a wind load calculation captures, and in the United States the numbers come from ASCE/SEI 7, the standard for minimum design loads on buildings.

The method is a chain of factors, each with a table behind it. A mapped basic wind speed for the site becomes a velocity pressure, adjusted for the roughness of the surrounding terrain, any hill the building stands on, and thinner air at altitude. That pressure is then turned into a design pressure on a particular wall, using coefficients for wind direction, gustiness, which face of the building it is, and the air pressure inside. Everything scales with the square of the wind speed, so the speed is the input to get right: an error of 10% in it becomes an error of 21% in the load.

The calculator follows ASCE 7-22, the 2022 edition, and covers walls only, at the level of the main wind force resisting system: the frames, shear walls and diaphragms that carry the whole building's wind load to the foundation. It gives no roof pressures or uplift, and none of the higher local pressures that govern windows, cladding panels and fasteners.

ASCE 7 is a standard, not a law. It becomes binding when a building code adopts it, as the International Building Code does for wind in §1609.1.1, and the edition and wind map in force where you build may be older than 7-22, with local amendments on top. Use the results to understand a design or to start one; a licensed structural engineer must confirm any real design and sign it off before work proceeds.

What is wind load calculator?

Wind load is the pressure moving air exerts on a surface, in pounds per square foot (psf), and the total force that pressure produces over an area, in pounds. On an enclosed building it acts on both sides of every wall. Outside, the wind presses on the face it strikes and pulls on the faces where the airflow breaks away. Inside, air leaking in through doors, windows and gaps raises or lowers the pressure on every wall at once.

ASCE 7 divides the calculation in two. Chapter 26 turns the mapped wind speed into a velocity pressure q, the dynamic pressure of the wind at the building's height. Chapter 27 turns q into a design pressure p on a particular surface.

The standard also separates the main wind force resisting system (MWFRS), which collects load over large areas, from components and cladding, which feel sharper local peaks, especially near corners and edges. The figures here are MWFRS wall pressures: right for checking a shear wall or a frame, wrong for choosing a window anchor or a siding fastener.

How to use this calculator.

1. 01Look up the basic wind speed V for the exact site in the ASCE 7 Hazard Tool or on the map your jurisdiction has adopted, for the building's Risk Category. It is a 3-second gust in mph; never estimate it.
2. 02Choose the exposure. B needs closely spaced obstructions the size of houses or larger over a long distance upwind; a house at the edge of a subdivision facing an open field is exposure C from that side. Picking B where C applies cuts the pressure by about 29% at 30 ft.
3. 03Enter the mean roof height, the average of eave and ridge measured from the ground (for roofs pitched at 10° or less the eave height may be used), and the ground elevation if you know it. Leave elevation at 0 otherwise; a factor of 1.0 is always permitted.
4. 04Leave Kzt at 1.0 unless the building sits on or near the crest of an isolated hill, ridge or escarpment, and G at 0.85 unless the building is flexible, with a natural frequency below 1 hertz. Either special case needs values worked out separately under the standard.
5. 05Set the enclosure and the plan ratio L/B, the building's dimension along the wind divided by its dimension across it. Partially enclosed is a specific classification for a building with a large dominant opening, not a description of a draughty one.
6. 06Pick the surface and the area. Choose one wall to design that wall, or the net across the building to size the lateral system, using the face area length × mean roof height. Then read the note under the result.

The formula.

Stage one is ASCE 7-22 Eq. 26.10-1: qh = 0.00256 × Kz × Kzt × Ke × V², with V in mph and qh in psf. The 0.00256 is half the density of standard sea-level air, 0.0765 lb/ft³ divided by the acceleration of gravity, multiplied by the square of the conversion from miles per hour to feet per second.

Kz describes how the wind picks up speed with height above the ground. Note 1 to Table 26.10-1 gives it as Kz = 2.01 × (z ÷ zg)^(2/α), where z is the mean roof height and α and zg come from Table 26.11-1: 7.0 and 1,200 ft for exposure B, 9.5 and 900 ft for C, 11.5 and 700 ft for D. Below 15 ft, z is held at 15, so a 10 ft building gets the same Kz as a 15 ft one. Rougher terrain slows the wind near the ground, so at 30 ft Kz is 0.7006 in exposure B, 0.9823 in C and 1.1622 in D. The ground elevation factor, Ke = exp(−0.0000362 × elevation in ft) from Table 26.9-1, is 1.0 at sea level and 0.8344 at 5,000 ft. Kzt is entered by you.

Stage two is Eq. 27.3-1: p = qh × Kd × G × Cp − qh × Kd × (GCpi). The directionality factor Kd = 0.85 (Table 26.6-1) allows for the strongest wind not always coming from the worst direction. G = 0.85 is the gust-effect factor for a rigid building (§26.11.1). Cp, from Fig. 27.3-1, is +0.8 on the windward wall, −0.7 on the side walls, and on the leeward wall −0.5 up to L/B = 1, −0.3 at 2 and −0.2 at 4 or more, interpolated in between. (GCpi), from Table 26.13-1, is ±0.18 for an enclosed building, ±0.55 for a partially enclosed one and 0 for an open one.

Both signs of (GCpi) have to be checked, and on a single wall one of them always adds to the outside load: internal suction when the outside is pushed in, internal pressure when the outside is sucked out. That governing sign is the one used. In the net-across mode the internal term pushes the windward and leeward walls in opposite directions and cancels, so the combined coefficient is simply 0.8 plus the size of the leeward Cp.

One simplification errs on the safe side. ASCE 7-22 evaluates the windward wall at qz, which grows with height up the wall; this calculator uses qh, the value at mean roof height, for every surface. Because Kz only increases with height, that overstates the windward pressure on the lower part of the wall, slightly on a low building and materially above about 60 ft, where the wall should be taken level by level.

A worked example.

Frequently asked questions.

References& sources.

1. [1]ASCE/SEI 7-22, Minimum Design Loads and Associated Criteria for Buildings and Other Structures — the primary source for every equation, table and figure on this page: Eq. 26.10-1 (velocity pressure), Table 26.6-1 (Kd = 0.85 for buildings), Table 26.9-1 (Ke = exp(−0.0000362 z)), Table 26.10-1 note 1 (Kz closed form), Table 26.11-1 (terrain exposure constants α and zg), §26.11.1 (G = 0.85 for rigid buildings), §26.12 (enclosure classification), Table 26.13-1 ((GCpi) = ±0.18 / ±0.55 / 0.00), Fig. 27.3-1 (wall external pressure coefficients) and Eq. 27.3-1 (design pressure). Authority: ASCE/SEI. Document revision: ASCE/SEI 7-22. Access: gated — the standard's text sits behind ASCE's paywall, so every figure attributed to it here is corroborated by at least two open reproductions listed below. Retrieved 2026-07-29.
2. [2]ASCE 7 Hazard Tool — the authoritative lookup for the basic wind speed V at a specific latitude and longitude, by ASCE 7 edition and Risk Category. This page requires the user to supply V from here or from the locally adopted map and never guesses it. Authority: ASCE/SEI. Document revision: live service covering ASCE 7-16 and 7-22. Locator: wind hazard by site coordinates. Access: open in a browser (registration prompted for saved reports); it is a client-rendered application and refuses automated retrieval (HTTP 403 on 2026-07-30). Retrieved 2026-07-29.
3. [3]MECA Enterprises, 'ASCE 7-22 Wind Load Changes' — documents that the directionality factor Kd was moved out of the velocity pressure equation and into the design pressure equations in ASCE 7-22, describes it as a technical change with no impact on loading in this edition, and explains the motivation (separate Kd values for internal and external pressure in future editions, and a distinct KdT for the new tornado provisions). This is the source for the edition conflict recorded on the page. Authority: MECA Enterprises (wind engineering software vendor). Document revision: ASCE 7-22 change summary. Retrieved 2026-07-29.
4. [4]Carlisle SynTec Systems, 'Adjustments Between ASCE 7-16 and ASCE 7-22' (SpecTopics, 20 February 2025) — an independent confirmation of the Kd relocation, of the unchanged internal pressure coefficients (0.18 enclosed, 0.55 partially enclosed), and of the change in wind speed map sets between the two editions. Authority: Carlisle SynTec Systems. Document revision: 2025-02-20. Retrieved 2026-07-29.
5. [5]Bentley Systems, STAAD.Pro Help v18, verification example 'V. ASCE 7-16 Wind Load Generation on Building'. Its published result for V = 108 mph, ground elevation 230 ft, mean roof height 40 ft, exposure B and Kzt = 1 is Kz = 0.761 and q = 19.14 lb/ft². This calculator returns Kz = 0.760609 and, once Kd is folded back in for the ASCE 7-16 arrangement, q = 19.1448 lb/ft². Result: agree, to three decimal places on Kz and four significant figures on q. Authority: Bentley Systems. Document revision: STAAD.Pro Help v18. Retrieved 2026-07-29.
6. [6]The Structural World, 'Guide to Wind Load Analytical Procedure of ASCE 7-10' (7 February 2019) — an open reproduction of the wall external pressure coefficients from Fig. 27.4-1/27.3-1 (windward +0.8 at qz; leeward −0.5 / −0.3 / −0.2 at L/B of 0–1 / 2 / ≥4 at qh; side wall −0.7 at qh), of G = 0.85 for rigid buildings, and of the terrain exposure constants α = 7 / zg = 1200 ft (B), 9.5 / 900 ft (C) and 11.5 / 700 ft (D) with Kz = 2.01 (z/zg)^(2/α). Used to corroborate the gated primary text. Authority: The Structural World. Document revision: ASCE 7-10, unchanged in these particulars through 7-22. Retrieved 2026-07-29.
7. [7]International Building Code 2021, §1609 'Wind Loads' — the adoption path that makes ASCE 7 legally operative: §1609.1.1 directs wind design to ASCE 7 and §1609.3 governs the basic wind speed. This is the basis for the statement beside the result that ASCE 7 is a standard rather than a law, that the adopted edition varies by jurisdiction, and that local amendments govern. Authority: International Code Council. Document revision: IBC 2021. Locator: §1609.1.1, §1609.3. Access: free to read on ICC Digital Codes in a browser, but automated retrieval is refused (HTTP 403 on 2026-07-30), so no value here is attributed to its text. Retrieved 2026-07-29.