💨 Wind & Location Parameters
mph
Enter wind speed 60–200 mph.
3-second gust. Use ASCE 7 wind map or hazards.atcouncil.org
ft
Enter height 5–500 ft.
Mean roof height or height where wind acts
ft²
Enter surface area in sq ft.
Area perpendicular to wind direction
Exposure C = most common default for open country
From ASCE 7-22 Table 27.4-1
Accounts for wind speed-up over hills and ridges
Design Wind Pressure
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⚠️ Engineering Disclaimer: This calculator uses simplified ASCE 7 methodology for preliminary estimation only. All structural wind load designs must be performed by or reviewed by a licensed structural engineer. Never use this result alone as the basis for a structural decision.
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Sources & Methodology
Wind load formulas verified against ASCE 7-22 Chapter 26–27 and IBC 2024 Section 1609. Kz values from ASCE 7-22 Table 26.10-1.
ASCE 7-22 — Minimum Design Loads and Associated Criteria
Primary U.S. standard for wind load design. Source for velocity pressure formula (Section 26.10), exposure coefficients Kz (Table 26.10-1), gust factor G = 0.85, and pressure coefficients Cp (Table 27.4-1).
IBC 2024 — International Building Code Section 1609
Adopts ASCE 7 by reference for wind load design. Provides wind speed maps and Risk Category requirements referenced in this calculator.
ATC Hazards by Location — ASCE 7 Wind Speed Lookup
Free Applied Technology Council tool to look up site-specific ASCE 7 design wind speeds for any U.S. address and Risk Category.
Methodology (ASCE 7-22):
qz = 0.00256 x Kz x Kzt x Kd x V^2 (velocity pressure, psf)
p = qz x G x Cp (design wind pressure, psf)
F = p x A (total wind force, lbs)
Kd = 0.85 (wind directionality factor). G = 0.85 (gust factor, rigid structures). Kz from ASCE 7-22 Table 26.10-1: linearly interpolated between tabulated height breakpoints for Exposures B, C, D. Negative pressure = suction (acts away from surface).
Last reviewed: April 2026 — ASCE 7-22 values
How Is Wind Load Calculated on a Building?
Wind load is the force exerted by moving air on a structure. Pressure increases as the square of wind speed — doubling wind speed quadruples wind pressure. ASCE 7 is the nationally recognized standard for calculating design wind loads in the United States, adopted by reference in the International Building Code (IBC 2024).
qz = 0.00256 x Kz x Kzt x Kd x V^2
Example — 115 mph, Exposure C, 20 ft, flat sign (Cp = 1.3):
Kz at 20 ft Exposure C = 0.90 • Kzt = 1.0 • Kd = 0.85
qz = 0.00256 × 0.90 × 1.0 × 0.85 × 115² = 25.9 psf
p = 25.9 × 0.85 × 1.3 = 28.6 psf
10 × 20 ft sign (200 sq ft): F = 200 × 28.6 = 5,720 lbs
Kz at 20 ft Exposure C = 0.90 • Kzt = 1.0 • Kd = 0.85
qz = 0.00256 × 0.90 × 1.0 × 0.85 × 115² = 25.9 psf
p = 25.9 × 0.85 × 1.3 = 28.6 psf
10 × 20 ft sign (200 sq ft): F = 200 × 28.6 = 5,720 lbs
ASCE 7 Exposure Categories and Kz Values
| Exposure | Description | Kz at 15 ft | Kz at 30 ft | Kz at 60 ft |
|---|---|---|---|---|
| B | Urban, suburban, wooded | 0.57 | 0.70 | 0.85 |
| C | Open terrain, scattered obstructions | 0.85 | 0.98 | 1.09 |
| D | Shorelines, flat water surfaces | 1.03 | 1.08 | 1.16 |
Design Wind Speeds by U.S. Region (Risk Category II)
| Region | Design Speed (mph) | Note |
|---|---|---|
| Central / Midwest U.S. | 90–105 | Tornado risk handled separately |
| Pacific Northwest / Mountain West | 95–115 | Elevation may increase local speeds |
| Gulf Coast (non-hurricane zone) | 110–130 | Verify with ASCE 7 map |
| Florida / Atlantic hurricane coast | 130–170 | Special high-wind provisions apply |
| Hawaii / U.S. Territories | 105–180+ | Island windward sides = Exposure D |
Wind Load on Rooftop Solar Panels
Rooftop solar panels experience both positive drag and negative uplift wind pressures. Edge and corner roof zones have higher local pressure coefficients (GCp) than the interior. In high-wind regions, uplift pressures can reach 30 to 60 psf. Racking attachments must transfer these forces into the roof structure. Engineering review is required for all solar installations in regions with design wind speeds above 110 mph.
Wind Load on Freestanding Signs and Fences
A freestanding wall or sign uses Cp = 1.3. At 90 mph in Exposure B at 6 ft height (Kz ≈ 0.57): qz = 0.00256 × 0.57 × 1.0 × 0.85 × 8,100 = 10.1 psf. Design pressure = 10.1 × 0.85 × 1.3 = 11.2 psf. A 6 × 8 ft fence panel (48 sq ft) sees approximately 540 lbs of lateral wind force. Post foundations must resist the resulting bending moment at grade.
💡 Find your site wind speed: Visit hazards.atcouncil.org and enter your address to get the exact ASCE 7-22 design wind speed for your location and Risk Category. This free tool removes guesswork and is the correct starting point for any wind load calculation.
Frequently Asked Questions
Wind load uses ASCE 7: velocity pressure qz = 0.00256 x Kz x Kzt x Kd x V^2 (psf). Then design pressure p = qz x G x Cp. Total force F = p x Area. G = 0.85 for rigid structures. Kz depends on terrain exposure and height. Cp depends on surface type (0.8 windward wall, 1.3 flat sign). Kd = 0.85 for most buildings.
ASCE 7 (Minimum Design Loads and Associated Criteria for Buildings) is the primary U.S. standard for wind load design, adopted by the International Building Code. It defines design wind speeds, exposure categories, the velocity pressure formula, and pressure coefficients for different building shapes. Any structural engineering involving wind loads in the U.S. must reference ASCE 7.
Exposure B: urban and suburban areas with many closely spaced obstructions such as houses and trees. Exposure C: open terrain with scattered obstructions under 30 feet, including grasslands and flat country. Exposure D: flat, unobstructed areas and water surfaces such as shorelines and tidal flats. Wind pressures are highest in Exposure D and lowest in Exposure B at equal heights.
The exposure coefficient Kz increases with height. In Exposure C, Kz goes from 0.85 at 15 ft to 1.09 at 60 ft to 1.26 at 160 ft. Since qz is proportional to Kz, wind pressure at 60 ft is about 28% higher than at 15 ft in Exposure C. Taller structures experience significantly greater wind pressures, especially in open terrain.
Velocity pressure qz is the dynamic pressure of moving air at a given height in psf. Formula: qz = 0.00256 x Kz x Kzt x Kd x V^2. The constant 0.00256 converts mph to psf. For 100 mph in Exposure C at 30 ft (Kz=0.98): qz = 0.00256 x 0.98 x 1.0 x 0.85 x 10,000 = 21.3 psf. This is the base from which design pressure is calculated.
Flat signs use Cp = 1.3. Design pressure p = qz x 0.85 x 1.3. At 100 mph, Exposure C, 20 ft (qz = 18.8 psf): p = 18.8 x 1.105 = 20.8 psf. A 10x20 ft sign (200 sq ft) sees 200 x 20.8 = 4,160 lbs total wind force. The sign structure and its mounting must be designed to safely resist this load plus appropriate safety factors.
Look up your exact value at hazards.atcouncil.org by entering your address and Risk Category. Most of the U.S. interior uses 90 to 115 mph. Coastal and hurricane-prone areas range from 130 to 180+ mph. Never assume a wind speed without checking the ASCE 7 wind map. Using an incorrect speed can significantly under- or over-estimate wind loads.
The gust factor G accounts for dynamic amplification of wind gusts. For rigid structures (natural frequency above 1 Hz), ASCE 7 allows G = 0.85 as a simplified constant. Flexible structures like tall buildings or long-span roofs require a dynamic gust factor calculation that accounts for resonance. For most low-rise buildings, G = 0.85 is appropriate and used in this calculator.
Roof-mounted solar panels experience both drag and uplift forces. Edge and corner zones have higher local pressure coefficients than interior zones. In high-wind regions, uplift pressures can reach 30 to 60 psf. Racking must resist both positive and negative pressures, with attachments adequate to transfer forces into the roof structure. Engineering review is required in regions with design speeds above 110 mph.
Yes for any structural application. This calculator provides preliminary estimates only. Licensed structural engineers are required by most jurisdictions for any structural work exposed to significant wind loads. Permits for exposed structures typically require stamped engineering drawings. A calculator alone is never sufficient basis for a structural construction decision.
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