Wind Load Calculator
The sky turned into pounds per square foot — velocity pressure from wind speed, then the wall force once gust and shape bite.
Wind Load Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Kzt, Kd, G, Cp pinned at low-rise common values
- Windward wall only — no leeward or internal pressure
In short: At 110 mph with a low-structure exposure coefficient of 0.70, the wind's velocity pressure reads about 18.4 psf. Apply the 0.85 gust factor and the 0.8 windward-wall shape and the wall feels about 12.5 psf — across a 900 ft² facade that is roughly 11,280 lb, five and a half tons of steady push that gusts multiply. Pressure grows with the square of speed: the 130 mph coast doubles what the 90 mph valley feels.
Formula
qz = 0.00256 · Kz · Kzt · Kd · V² · P = q·G·Cp
Velocity pressure is the kinetic energy of moving air, 0.00256 times the speed squared in mph units, trimmed or raised by height and terrain (Kz), topography (Kzt, flat 1.0) and directionality (Kd, 0.85). The wall pressure multiplies by the gust factor G and the shape coefficient Cp — 0.8 pushing on a windward wall. ASCE 7 names these factors; this screen holds them at their common low-rise values.
Worked Example
- Enter the design wind speed for your region.
- Pick the exposure coefficient for height and site.
- Read psf, then the tons on the wall.
Defaults: 110 mph, Kz 0.70, a 900 ft² wall — 18.43072 psf of velocity pressure, 12.53289 psf on the wall, about 5.64 tons of push. The same wall in a 150 mph zone takes nearly double the force.
Strengths & Limits Of This Model
Where this engine is strong
- Speed-squared visible in the arithmetic
- The constants are named, not buried
Where it stops
- Real studies pair windward, leeward and roof zones
Practical Use Cases
Cladding checks
psf before the panel spec
Sign and fence posts
the tons at the base
Storm planning
what the garage door must hold
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Wind Load Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Why does speed matter squared?
Wind pressure is kinetic energy density, and energy grows with the square of velocity. Double the speed and the push quadruples — the difference between a 90 mph valley and a 130 mph coast is not forty percent, it is about one hundred and nine.
What is the exposure coefficient doing?
Air slows near the ground and over rough terrain. Kz raises the pressure as the reference height climbs and the site opens: about 0.70 for a low-rise in suburban terrain, rising past 1.0 for tall work in the open.
What do the gust and shape factors mean?
G 0.85 discounts the rigid structure from the peak gust; Cp 0.8 says a windward wall takes eight-tenths of the stagnation pressure. Leeward walls see suction instead — the net load on the box is the difference of the two.
Is this the full ASCE 7 procedure?
No — it is the low-rise screen with Kzt, Kd, G and Cp pinned at their common values. Chapter 26 and 27 of the standard add topography, internal pressure and the leeward side; a stamped study replaces this page where it counts.
What about internal pressure?
A garage with big doors can pressurize inside while the windward wall is pushed outside — the net opening load adds an internal coefficient of up to 0.55 for partially enclosed buildings. This screen quotes the wall alone.
Why does the answer come in tons?
Because facades are big. Twelve and a half psf reads like a nothing until it multiplies by nine hundred square feet and arrives as five and a half tons leaning on the studs.
Does the leeward side get its own number?
It sees suction of about half the windward pressure, which is why roofs lift off rather than blow in. The full design pairs both faces; the screen gives the push that anchors and fasteners ask about first.
How do I choose the design wind speed?
From the wind maps in the building code for your risk category — coastlines run 130 to 180 mph, sheltered interiors nearer 90 to 110. The map value, not the last storm's memory, is the input this page wants.