Wind load comes down to two equations and a handful of table look-ups. This guide walks the full ASCE 7-22 method — risk category, basic wind speed, exposure, the velocity pressure qz, and the coefficients that turn it into a design pressure in psf — then shows the one-click shortcut when you'd rather not read tables.
Every ASCE 7-22 wind load is built in two moves: first the velocity pressure the wind carries, then the pressure that lands on a particular surface. Get these two and the rest is table look-ups.
qz = 0.00256 · Kz · Kzt · Kd · Ke · V²
p = qz · ( GCp − GCpi )
p = q · G · Cp − qi · (GCpi)
Eight moves take you from a dot on the map to a signed pressure in psf. Do them in order and nothing gets skipped.
Classify the building I–IV by occupancy. A hospital is Risk IV; a shed is Risk I. The category picks which wind-speed map you read.
Read V (mph) from the ASCE 7-22 map for that risk category — or look it up by ZIP so you skip tracing contours by eye.
Assign B, C, or D from the ground roughness upwind. Suburbs are usually B; open country and coastline push toward C and D.
Look up Kz from Table 26.10-1 for the exposure and the evaluation height. Taller and more open both raise it.
Set the topographic factor (1.0 on flat terrain), directionality (0.85 for buildings), and the ground elevation factor.
Multiply it out: qz = 0.00256·Kz·Kzt·Kd·Ke·V². Now you have psf at that height.
Read GCp (or Cp for MWFRS) for the surface and zone, and GCpi for the enclosure class.
Combine: p = qz(GCp − GCpi) for C&C, or the Chapter 27 combination for MWFRS. That is your design pressure.
One enclosed building, run all the way through. Swap in your own numbers and the shape of the arithmetic never changes.
Say the mapped basic wind speed at the site is V = 150 mph, the mean roof height is 30 ft, the exposure is C, the ground is flat, and the building is enclosed. Read the coefficients:
qz = 0.00256 · 0.98 · 1.0 · 0.85 · 1.0 · 150² ≈ 48.0 psf
Now turn that into a wall-corner design pressure. For an enclosed building GCpi = ±0.18. Take a Zone 5 (corner) external coefficient of GCp = −1.1 — illustrative; the exact value comes from Figure 30.3-1 for your zone and effective wind area:
p = 48.0 · ( −1.1 − 0.18 ) ≈ −61 psf (suction)
The surface you are designing decides the coefficients — and usually a real project needs more than one.
Components & cladding pressures by zone and effective wind area — the numbers you match to a product approval. See the C&C wind load guide.
Gable, hip, monoslope, and flat roofs, plus overhangs — where corner and edge suction decides membranes, panels, and fasteners.
Directional pressures on every wall and the roof — the loads the frame, connections, and foundation are sized to carry.
Force coefficients for solid and open signs, freestanding walls, rooftop equipment, chimneys, and towers under Chapter 29.
Rooftop and ground-mount PV arrays, parapets, and attached canopies — each with its own ASCE 7-22 procedure.
The method above is exact — the tedium is reading Kz, GCp, and GCpi right for every zone. That is what the calculator removes.
Two moves. First the velocity pressure: qz = 0.00256·Kz·Kzt·Kd·Ke·V², where V is the basic wind speed in mph and qz lands in psf. Then the design pressure: for components & cladding, p = qz(GCp − GCpi); for the MWFRS, the external and internal pressures are combined per ASCE 7-22 Chapter 27.
The basic wind speed comes from the ASCE 7-22 wind maps, and there is a separate map for each risk category. Rather than trace contour lines, enter a ZIP or address and read the mapped speed directly — with the enforceable Florida value applied in Miami-Dade and Broward.
Components & cladding pressures size the individual pieces — a window, a door, a roof panel, a fastener — using GCp by zone and effective wind area. MWFRS pressures are the whole-building loads the frame resists, using Cp on each face. A real project usually needs both.
For current permits, ASCE 7-22 — the edition Florida's 8th-Edition Building Code and most other state codes now enforce. Our calculators are 7-22 end to end: maps, coefficients, and equations all track the current standard.
Yes — every step here can be done by hand with the ASCE 7-22 tables and maps. The work is in reading Kz, Kzt, GCp, and GCpi correctly for each zone and effective wind area, and keeping the enclosure and risk category consistent. That is exactly what the calculator automates.
Design wind pressure is in pounds per square foot, psf. Positive pushes on a surface; negative (suction) pulls away from it. Roof corners and wall edges usually see the largest suction.
The math can be, but the plans examiner wants the work shown. The calculator produces an Engineering Report with every coefficient cited to its ASCE 7-22 section. That report is not a sealed document — a PE sign-and-seal is a separate service, available in all 50 states.
You now have the whole method — risk category, wind speed, exposure, qz, and the coefficients that give you psf. When you want the answer without the look-ups, the wind load pressure calculator runs all eight steps from a single address.
The ASCE 7-22 guide covers the chapters and figures behind each coefficient, and the free MWFRS calculator runs the whole-building side.
Open the free calculator →