Free MWFRS Wind Load Calculator · ASCE 7-22 Directional · No signup

MWFRS wall & roof pressures,
the whole building at once.

A free online MWFRS wind load calculator: enter a ZIP and a building box and get ASCE 7-22 directional pressures on the windward wall, leeward wall, side walls, and roof — every coefficient cited to its section.

Quick answer: Yes — this is a free MWFRS wind load calculator. Enter a U.S. ZIP and building dimensions and it returns the ASCE 7-22 directional Main Wind Force Resisting System pressures (psf) for a low-rise building — the wind speed is looked up for you, no signup.

Directional procedure (Ch. 27) Every coefficient cited Wind speed by ZIP, built in

Calculating wind loads since 2002, online since 2006.

One of the very first wind load calculators on the web 7 ASCE editions navigated (7-95 → 7-22) In-house FL-licensed P.E.

Try it live — surface pressures update as you type.

The same ASCE 7-22 directional engine the paid MWFRS product runs, one building box at a time. For the envelope procedure, every roof geometry, topographic effects, and a full engineering report, get the full MWFRS calculator →

Inputs

ZIP Code 5-digit US ZIP

Risk Category ASCE 7-22 Table 1.5-1

Essential facilities (hospitals, schools, emergency response) require the full MWFRS calculator.

Exposure Category ASCE 7-22 §26.7

Enclosure ASCE 7-22 §26.13

Mean Roof Height feet (low-rise ≤ 60)

Building Plan Dimensions feet

B = wall width facing the wind · L = depth parallel to the wind.

Roof Slope degrees (0 = flat)

Wind Direction Fig 27.3-1

Design Pressure — idle

Max positive (pressure)

—.—psf

Max negative (suction)

—.—psf

Enter a ZIP and your inputs — the result appears here live.

Coefficient	Value	Reference
Calculation pending — enter your inputs above.

Need the full MWFRS design, not just a screen?

The paid MWFRS calculator adds the envelope procedure, every roof geometry, topographic (Kzt) effects, saved projects, Excel export, and a full engineering report — with no daily cap.

Get the MWFRS calculator →

How it works

From ZIP to surface pressures in four steps.

No email gate, no manual wind-speed lookup. The same ASCE 7-22 directional engine engineers pay for, run on one building box so you can check a number in seconds.

Enter the project ZIP

The calculator pulls the ASCE 7-22 basic wind speed for the site and Risk Category, so you never read V off a map by hand.

Pick Risk Category & Exposure

Risk Category I–IV per ASCE 7-22 Table 1.5-1 sets V; Exposure B/C/D per ASCE 7-22 §26.7 sets the K_z profile.

Describe the building box

Mean roof height h, plan dimensions B × L, roof slope, enclosure, and wind normal or parallel to the ridge.

Read every surface

Directional pressures in psf for windward wall, leeward wall, side walls, and roof. Expand the math to see q_h, G, and each C_p with its reference.

Free vs. full

What the free screen does — and where the paid calculator takes over.

The free screen runs the real ASCE 7-22 directional procedure on one low-rise box so you can check pressures fast. The paid MWFRS calculator is the tool you design and submit with.

Capability	Free screen	Full MWFRS calculator
Directional procedure (Ch. 27)	Yes	Yes
Envelope procedure (Ch. 28)	—	Yes
Building height	≤ 60 ft (low-rise)	Any height
Roof geometry	flat / gable / hip	All shapes
Topographic factor K_zt	1.0 (flat)	Full K_zt
Exposure B, Risk Cat III & IV	—	Yes
Saved projects & Excel export	—	Yes
Full engineering report (PDF)	—	Yes
Daily limit	10 / day	Unlimited

Every value on the free screen cites its ASCE 7-22 source, so what you see here is the same math the paid tool runs — just scoped to one building. See the full MWFRS calculator →

Directional procedure

The four surfaces the directional procedure loads.

For wind from one direction, ASCE 7-22 Figure 27.3-1 assigns each building surface an external pressure coefficient C_p. The pressure on each is p = qGC_p − q_i(GC_pi).

Windward wall · C_p = +0.8: The wall facing the wind, pushed inward. Uses q_z evaluated at the height in question, so it grows with height up the wall.
Leeward wall · C_p = −0.5 to −0.2: The wall away from the wind, suction. The exact value depends on the L/B ratio (−0.5 at L/B ≤ 1, −0.2 at L/B ≥ 4). Uses q_h.
Side walls · C_p = −0.7: The walls parallel to the wind, steady suction along their length. Uses q_h.
Roof · C_p by h/L and θ: Windward and leeward roof coefficients depend on the h/L ratio and roof angle θ — typically uplift on a low-slope roof, easing as the slope steepens. Uses q_h.

Methodology

How the MWFRS pressures are calculated.

Per the ASCE 7-22 Chapter 27 directional procedure, the pressure on each MWFRS surface is:

p = q G C_p − q_i (GC_pi) (Eq. 27.3-1)

Where the velocity pressure is

q_h = 0.00256 × K_z × K_zt × K_d × K_e × V² (Eq. 26.10-1)

Coefficients

V — Basic wind speed (mph). ASCE 7-22 Figure 26.5-1, looked up from the project ZIP by Risk Category.
q, q_h — Velocity pressure; windward wall uses q_z at the surface height, all other surfaces use q_h at the mean roof height.
G — Gust-effect factor. ASCE 7-22 §26.11 (0.85 for a rigid building).
C_p — External pressure coefficient per surface. ASCE 7-22 Figure 27.3-1 (walls by L/B; roof by h/L and roof angle θ).
K_z — Velocity pressure exposure coefficient. ASCE 7-22 Table 26.10-1, varies with height and Exposure Category.
K_zt — Topographic factor. ASCE 7-22 §26.8.2 (fixed at 1.0 on this free screen; full K_zt in the paid calculator).
K_d — Wind directionality factor. ASCE 7-22 Table 26.6-1 (0.85 for MWFRS of buildings).
(GC_pi) — Internal pressure coefficient. ASCE 7-22 Table 26.13-1, by enclosure classification.

Sources

Where the numbers come from.

Every value returned by this calculator traces to a published standard or code. Verified as of 2026.

ASCE/SEI 7-22 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (2022 edition). American Society of Civil Engineers. Chapters 26 and 27 (directional procedure).
Florida Building Code, 8th Edition (2023) Residential R301.2(7) jurisdictional wind speed amendments. Florida Department of Business and Professional Regulation.
International Building Code 2024 Adopts ASCE 7-22 by reference (Section 1609).
USPS ZIP Code Database 33,783 5-digit US ZIP codes with city, county, state, and centroid coordinates.
In-house Florida-licensed Professional Engineer Reviews jurisdictional override values against current FBC text.

Frequently asked

Common questions.

What is MWFRS in wind load design?▾

MWFRS stands for the Main Wind Force Resisting System — the assembly of structural elements (frames, shear walls, diaphragms, the roof deck acting as a diaphragm) that receives wind load from more than one surface and carries it to the foundation. ASCE 7-22 treats it separately from Components and Cladding: MWFRS sizes the overall lateral system, while C&C sizes individual pieces like windows and fasteners. This free calculator solves the MWFRS directional procedure of ASCE 7-22 Chapter 27.

Is this free MWFRS wind load calculator really free?▾

Yes. Enter a ZIP and a building box and it returns the directional MWFRS wall and roof pressures on screen, free, with no signup — up to 10 calculations per day. The paid MWFRS calculator removes the daily cap and adds the envelope procedure, all roof geometries, topographic (K_zt) effects, saved projects, Excel export, and a full engineering report. The free screen is a genuine slice of the same engine, not a teaser that hides the math.

What is the difference between the directional and envelope procedures?▾

ASCE 7-22 gives two ways to find MWFRS pressures on a low-rise building. The directional procedure (Chapter 27) applies pressure coefficients C_p to each building surface for wind from a given direction — it is what this free tool runs. The envelope procedure (Chapter 28) instead applies pseudo-pressure coefficients GC_pf that envelope the worst-case load cases as the wind rotates. Both are code-compliant for buildings h ≤ 60 ft; the envelope procedure is in the paid calculator.

How are MWFRS wall and roof pressures calculated in ASCE 7-22?▾

Per ASCE 7-22 Equation 27.3-1, p = qGC_p − q_i(GC_pi). q is the velocity pressure (q = 0.00256·K_z·K_zt·K_d·K_e·V²), G is the gust-effect factor (0.85 for a rigid building), C_p is the external pressure coefficient for each surface from Figure 27.3-1, and GC_pi is the internal pressure coefficient from Table 26.13-1. Windward wall uses q_z at the surface height; leeward wall, side walls, and roof use q_h at the mean roof height.

What Cp values does the directional procedure use for walls?▾

From ASCE 7-22 Figure 27.3-1: the windward wall uses C_p = +0.8, the side walls use C_p = −0.7, and the leeward wall uses C_p between −0.5 and −0.2 depending on the L/B ratio (−0.5 for L/B ≤ 1, −0.3 at L/B = 2, −0.2 for L/B ≥ 4, interpolated between). Roof C_p depends on the h/L ratio and the roof angle θ. This calculator shows the C_p it used for each surface.

Does this MWFRS calculator look up the wind speed for me?▾

Yes. Enter the project ZIP and the calculator returns the ASCE 7-22 basic wind speed for that location and Risk Category from a pre-computed database of all US ZIP codes, so you do not read V off a map by hand. Many free MWFRS tools make you look up and type V yourself, which is a common source of error.

What building sizes does the free MWFRS screen support?▾

The free screen covers enclosed and partially enclosed low-rise buildings with a mean roof height of 60 ft or less and a regular rectangular footprint, on flat terrain (K_zt = 1.0). Taller buildings, open buildings, irregular geometry, and real topographic effects are handled in the paid MWFRS calculator.

What does "wind normal to the ridge" versus "parallel to the ridge" mean?▾

The directional procedure checks wind blowing perpendicular to the ridge line (normal) and along the ridge line (parallel) because the roof pressure coefficients differ between the two. For a gable or hip roof the governing case is often wind normal to the ridge; for the walls the windward/leeward split simply follows the wind direction. Toggle the two on the calculator to compare.

Is MWFRS the same as Components and Cladding (C&C)?▾

No. MWFRS sizes the overall structure that resists wind from multiple surfaces at once, using lower area-averaged pressures. C&C sizes individual elements (windows, doors, fasteners, roof panels) that feel higher localized peak pressures over small tributary areas. A complete design checks both. Use this page for MWFRS; use our free C&C calculator for a single window or wall component.

Can I use this MWFRS output for a building permit?▾

The pressures are computed with the same ASCE 7-22 directional engine as our paid product and every coefficient is cited, so they are suitable for checking and preliminary design. The paid MWFRS calculator produces a full engineering report with the calculations laid out for review. Any requirement for a licensed professional engineer's involvement is handled separately by our engineers, not by the software. Treat the free screen as a fast, defensible screening tool, not a final report.