What is the ASCE 7 simplified wind load procedure?

ASCE 7 Chapter 27 provides a simplified method for low-rise buildings (h ≤ 60 ft). It uses the velocity pressure equation qh = 0.00256 × Kh × Kzt × Kd × V² × I to compute design pressures for walls and roof zones.

What is Exposure Category B, C, or D?

Exposure B is suburban terrain with obstructions (houses, trees). Exposure C is open terrain with scattered obstructions. Exposure D is coastal terrain within one mile of water. Higher exposure categories produce greater wind pressures.

What wind speed should I use?

Use the design wind speed from ASCE 7-16 Figure 26.5-1A/1B/1C for your location and occupancy category. Common U.S. values range from 85 mph in the central U.S. to 140+ mph along Gulf and Atlantic coasts.

Wind Load Calculator | ASCE 7 Wind Pressure & Base Shear

Zone	Pressure (psf)	Area (ft²)	Force (kips)
Windward Wall	—	—	—
Leeward Wall	—	—	—
Side Wall	—	—	—
Roof (windward)	—	—	—

Region	Typical V (mph)	Notes
Midwest / Great Plains	85–95	Low-hazard, flat terrain
Pacific Northwest / Mountain West	85–100	Varies by elevation
Mid-Atlantic / New England	100–110	Coastal influence increases toward shore
Southeast (inland)	100–115	Higher near Gulf / Atlantic coast
Gulf Coast (TX, LA, MS, AL)	120–140	Hurricane zone
Florida (Atlantic coast)	120–150	Miami-Dade: up to 170 mph
Hawaii	130–160	Higher on windward exposures
Puerto Rico	145–175	Eastern tip highest

Height (ft)	Exposure B	Exposure C	Exposure D
0–15	0.57	0.85	1.03
20	0.62	0.90	1.08
25	0.66	0.94	1.12
30	0.70	0.98	1.16
40	0.76	1.04	1.22
50	0.81	1.09	1.27
60	0.85	1.13	1.31

Surface	L/B Ratio	GCp (windward)	GCp (leeward)
Windward wall	All	+0.8	—
Leeward wall	0–1	—	−0.5
Leeward wall	2	—	−0.3
Leeward wall	≥ 4	—	−0.2
Side walls	All	−0.7
Roof (flat, 0–5°)	All	−0.9 to −0.18
Roof (low slope, 6–20°)	All	−0.5 / +0.2	−0.6
Roof (medium, 21–35°)	All	+0.2	−0.6
Roof (steep, >35°)	All	+0.8	−0.6

Risk Category	I_w	Typical Occupancy
I	0.87	Storage, agriculture, minor facilities
II	1.00	Residential, commercial, office
III	1.15	Assembly (>300), schools, jails
IV	1.15	Hospitals, emergency facilities, power plants

Region	V (mph)	Exposure	h (ft)	Windward (psf)	Base Shear*
Kansas City, MO	90	C	20	14.0	Low
Charlotte, NC	100	B	20	12.9	Moderate
Atlanta, GA	100	B	20	12.9	Moderate
Houston, TX	130	C	20	32.7	High
Miami, FL	175	D	20	76.2	Very High
New Orleans, LA	140	D	20	49.0	High
Seattle, WA	85	B	20	10.2	Low
Honolulu, HI	130	C	20	32.7	High

1

Select basic wind speed

Choose the design wind speed from the dropdown using ASCE 7-16 Figure 26.5-1 for your location and Risk Category, or enter a custom value in mph.

2

Choose exposure category

Select B (suburban), C (open terrain), or D (coastal) based on your site's surface roughness for at least 1,500 feet upwind.

3

Enter building dimensions

Input mean roof height (maximum 60 ft for the simplified procedure), building length, and building width.

4

Select roof slope and occupancy

Choose your roof pitch and occupancy category so the calculator can apply the correct importance factor automatically.

5

Review results

Compare velocity pressure qh, design pressures for all zones, and total base shear, then switch to Pressure Map for a visual diagram.

Velocity Pressure (qh)

qh = 0.00256 × Kh × Kzt × Kd × V² × Iw

Kh is the velocity pressure exposure coefficient at mean roof height; Kzt is the topographic factor (1.0 for flat terrain); Kd is the directionality factor (0.85 for buildings); V is basic wind speed in mph; Iw is the importance factor based on Risk Category.

Net Design Pressure (windward wall)

p = qh × G × Cp + qh × GCpi

qh is velocity pressure; G is the gust factor (0.85 for rigid buildings); Cp is the external pressure coefficient for the surface; GCpi is the internal pressure coefficient (±0.18 for enclosed buildings).

Height Interpolation Factor (T)

T = (h − heights[i]) / (heights[i+1] − heights[i])

h is actual mean roof height in feet; heights[i] and heights[i+1] are the table reference heights bracketing h; T is used to linearly interpolate the exposure coefficient Kh between tabulated values.

Exposure Category A classification of the terrain surrounding a building site that affects wind speed and turbulence. Category B is suburban, C is open country, and D is coastal — each results in different velocity pressure coefficients.

Velocity Pressure (qh) The dynamic pressure of the wind at mean roof height, measured in pounds per square foot. It is the baseline from which all surface design pressures are calculated.

Roof Slope The pitch of the roof expressed as inches of rise per 12 inches of horizontal run. Roof slope affects the external pressure coefficients for roof surfaces, especially at low slopes where uplift is most severe.

Occupancy / Risk Category A classification of buildings by consequence of failure. Category I is low-hazard storage; Category II is most buildings; Category III is high-occupancy; Category IV is essential facilities — higher categories use larger importance factors.

Topographic Factor (Kzt) A multiplier that accounts for wind speed-up over hills, ridges, and escarpments. It equals 1.0 for flat terrain and can increase to 1.5 or more for buildings near hilltops or escarpments per ASCE 7-16 Section 26.8.

MI

Mike — Suburban Office Building

Single-story office in suburban terrain

Basic Wind Speed 115 mph (Risk Cat. II) Exposure Category B (suburban) Mean Roof Height 18 ft Roof Slope 4/12

Result: qh ≈ 20.4 psf. Windward wall design pressure ≈ 15.8 psf; leeward wall ≈ −10.2 psf; total base shear depends on wall area. Use these values as input to your lateral load design — confirm with a licensed engineer for permit submissions.

JE

Jessica — Coastal Retail Store

Single-story retail building near the coast

Basic Wind Speed 140 mph (Risk Cat. II) Exposure Category D (coastal) Mean Roof Height 24 ft Roof Slope 2/12 (flat)

Result: qh ≈ 45.6 psf — more than double the suburban result due to higher speed and Exposure D. Roof uplift pressure exceeds 30 psf in corner zones, requiring uplift straps and enhanced fastening. A licensed structural engineer must review this design before permit application.

Wind load determines how much lateral and uplift force your building structure must resist during a storm. Calculating it correctly requires knowing your design wind speed, site terrain, building dimensions, and roof shape. This guide explains the ASCE 7 simplified procedure used in this calculator, how each input affects the result, and when you need a licensed engineer to take over from a preliminary estimate.

How Wind Speed Translates to Pressure

Wind speed alone does not tell you the force on a building. Velocity pressure (qh) converts the kinetic energy of moving air into a force per square foot using the formula qh = 0.00256 × Kh × Kzt × Kd × V² × Iw. The V² term means pressure increases with the square of wind speed — doubling wind speed quadruples the pressure. A 140-mph hurricane generates roughly four times the pressure of a 70-mph thunderstorm.

The exposure coefficients Kh and Kzt modify velocity pressure based on terrain roughness and topography. Buildings in open coastal terrain (Exposure D) experience significantly higher pressures than identical buildings in suburban areas (Exposure B) at the same wind speed. This is why coastal construction codes are so much more demanding than inland standards — it is not simply about higher design wind speeds, but also about the terrain multipliers that amplify those speeds into larger surface pressures.

Pressure Zones and Why They Matter

Wind does not push uniformly on a building. Windward walls experience positive (inward) pressure; leeward walls and side walls experience negative (suction) pressure. Roof surfaces experience suction on most slopes, with the highest uplift forces occurring in the corners and edges of the roof where airflow accelerates around the building perimeter. These corner zones can see two to three times the pressure of the roof field area.

Design pressure for each surface is calculated as p = qh × G × Cp ± qh × GCpi, where Cp is the external pressure coefficient for that surface and GCpi is the internal pressure coefficient. The internal pressure adds or subtracts depending on the opening condition of the building. An enclosed building with a few windows has GCpi = ±0.18; a building with a large opening on the windward wall can reach GCpi = ±0.55, dramatically increasing loads on internal surfaces and connections.

Limitations of the Simplified Procedure

This calculator applies the ASCE 7-16 simplified procedure from Chapter 27, which is valid only for low-rise buildings with mean roof height not exceeding 60 feet and a height-to-least-plan-dimension ratio not greater than 1.0. Buildings outside these limits require the full directional or envelope procedure, which accounts for height-varying pressures and more complex aerodynamic behavior. Tall, slender buildings and irregular plan shapes always require the full procedure.

Even within the simplified procedure's limits, this calculator produces preliminary design values for educational and planning purposes. Permit applications require calculations stamped by a licensed structural engineer, who will also check load combinations per ASCE 7-16 Section 2.3 (LRFD) or 2.4 (ASD), verify connection details, and confirm that wind does not govern over seismic in high-seismicity zones. Use these results to size preliminary members and get a sense of the load magnitude — then hand the project to an engineer for the formal design.

Is this calculator valid for code submissions?+

This calculator uses the ASCE 7-16 simplified procedure for educational and preliminary design purposes only. For permit applications, a licensed structural engineer must apply the full ASCE 7 directional or envelope procedure and stamp the calculations. Confirm requirements with your local authority having jurisdiction before submitting plans.

Why is the height limit 60 feet?+

The ASCE 7 simplified procedure (Part 1 of Chapter 27) applies only to low-rise buildings with mean roof height h ≤ 60 ft and h/L ≤ 1. Taller buildings require the full directional procedure with height-varying pressures and more complex aerodynamic shape factors. Enter a building taller than 60 feet and this calculator will flag the input as out of range.

What is topographic factor Kzt and when does it change?+

Kzt accounts for wind speed-up over hills, ridges, and escarpments per ASCE 7-16 Section 26.8. It equals 1.0 for flat terrain, which is the default in this calculator. Buildings near hilltops or escarpments can have Kzt values of 1.5 or more, so you should calculate the actual value using Figure 26.8-1 if your site is near elevated terrain.

Should I use wind load or seismic base shear for design?+

Apply whichever base shear is larger after combining loads per the governing load combinations in ASCE 7-16. In hurricane-prone coastal zones, wind typically controls lateral design. In seismically active regions like California or the Pacific Northwest, seismic loads often govern. Always check both and use the larger value — you cannot assume one will always control.

What GCpi value is used for internal pressure?+

This calculator uses GCpi = ±0.18 for enclosed buildings per ASCE 7-16 Section 26.13.2. The sign is chosen to maximize net pressure for each surface. Partially enclosed buildings (large openings on windward face) use GCpi = ±0.55 and require a separate analysis not covered by this simplified tool.

How do I determine the correct exposure category?+

Stand at the building site and assess the upwind surface roughness for at least 1,500 feet in the direction of the prevailing storm wind. Suburban areas with trees and houses are Exposure B; open flat terrain with scattered obstructions is Exposure C; and coastal areas with water or flat open country for 1 mile or more are Exposure D. When the terrain falls between categories, use the more severe one.

Wind Load Calculator

Building Parameters

Wind Pressure Zone Diagram

Force Breakdown

Basic Wind Speed V (ASCE 7-16)

Exposure Category Definitions (ASCE 7-16 §26.7)

Velocity Pressure Exposure Coefficient K_h (ASCE 7-16 Table 26.10-1)

External Pressure Coefficients GCp (ASCE 7-16 §27.3)

Importance Factor I_w (ASCE 7-16 Table 1.5-2)

Key Equations (ASCE 7-16)

Common Design Pressures by Region

How to Use This Calculator

Select basic wind speed

Choose exposure category

Enter building dimensions

Select roof slope and occupancy

Review results

Formula & Methodology

Key Terms Explained

Real-World Examples

Mike — Suburban Office Building

Jessica — Coastal Retail Store

Understanding Wind Load on Buildings

How Wind Speed Translates to Pressure

Pressure Zones and Why They Matter

Limitations of the Simplified Procedure

Frequently Asked Questions

Wind Load Calculator

Building Parameters

Wind Pressure Zone Diagram

Force Breakdown

Basic Wind Speed V (ASCE 7-16)

Exposure Category Definitions (ASCE 7-16 §26.7)

Velocity Pressure Exposure Coefficient Kh (ASCE 7-16 Table 26.10-1)

External Pressure Coefficients GCp (ASCE 7-16 §27.3)

Importance Factor Iw (ASCE 7-16 Table 1.5-2)

Key Equations (ASCE 7-16)

Common Design Pressures by Region

How to Use This Calculator

Select basic wind speed

Choose exposure category

Enter building dimensions

Select roof slope and occupancy

Review results

Formula & Methodology

Key Terms Explained

Real-World Examples

Understanding Wind Load on Buildings

How Wind Speed Translates to Pressure

Pressure Zones and Why They Matter

Limitations of the Simplified Procedure

Frequently Asked Questions

Keep Exploring

Related calculators

Guides & articles

Velocity Pressure Exposure Coefficient K_h (ASCE 7-16 Table 26.10-1)

Importance Factor I_w (ASCE 7-16 Table 1.5-2)