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    Calculates locally in your browser · ASCE 7 velocity pressure
    Wind / design pressure

    ASCE 7 wind load calculator

    Wind pressure is not linear in speed: it rises with the square of velocity, so a 20% stronger gust adds 44% to the load. This calculator applies the ASCE 7 velocity-pressure equation, subtracts internal pressure, and converts the result into a force on the tributary area.

    Kz1.00ExposureOpenCp0.80
    Velocity pressure qz
    1055 N/m²
    At V = 45 m/s
    Design pressure
    0.528 kPa
    inward on the windward face
    Force on tributary area
    5.3 kN
    Over 10.0 m²
    Leeward pressure
    -0.638 kPa
    Negative: suction
    Pressure build-up
    Every factor in the ASCE 7 velocity-pressure equation.
    1055 N/m²
    Pressure build-up
    TermValue
    Basic wind speed V45 m/s
    Exposure coefficient Kz1.00
    Topographic factor Kzt1.00
    Directionality Kd0.85
    Gust factor G0.85
    Velocity pressure qz1055 N/m²
    External Cp0.80
    Internal GCpi0.18
    Net pressure p528 N/m²

    Pressures are strength-level and must be combined with dead and live load cases.

    Inspect the model
    Choose a quick result view, a scaled comparison, or the complete diagnostic set.
    Pressure against wind speed
    Pressure rises with the square of velocity — a 20% gust adds 44% to the load.
    Pressure against wind speed0.0000.3030.6050.9081.211.5118182323292934344040454550505656616167677272kPa
    Windward against leeward
    The two faces act together on the building envelope.
    Windward against leeward-0.732-0.438-0.1440.1500.4440.7370.528WindwardWindward-0.638LeewardLeewardkPa
    Canonical equations
    The exact relationships implemented by this engine.

    qz = 0.613·Kz·Kzt·Kd·V² · SI form; V in m/s gives N/m².

    p = qz·G·Cp − qh·GCpi · External pressure less internal pressure.

    F = p·A · Applied to the tributary area of the element.

    engineering methodology

    A clear path from inputs to results.

    Wind pressure is not linear in speed: it rises with the square of velocity, so a 20% stronger gust adds 44% to the load. This calculator applies the ASCE 7 velocity-pressure equation, subtracts internal pressure, and converts the result into a force on the tributary area.

    Step-by-step methodWorked exampleAssumptions explained

    How to use

    1. Enter the basic wind speed for the site.
    2. Set the exposure coefficient for the height and terrain.
    3. Apply the topographic and directionality factors.
    4. Enter the pressure coefficients and the tributary area.

    The formula

    qz=0.613KzKztKdV2,p=qzGCp−qzGCpiq_z = 0.613 K_z K_{zt} K_d V^2, \qquad p = q_z G C_p - q_z GC_{pi}

    Reference: ASCE 7-22 Chapter 26 (velocity pressure) and Chapter 27 (main wind-force-resisting system).

    Worked example

    45 m/s, Kz 1.0, Cp 0.8, GCpi 0.18

    Inputs
    • V = 45 m/s.
    • Kz = 1.0, Kzt = 1.0, Kd = 0.85, G = 0.85.
    • Cp = 0.8, GCpi = 0.18.
    • Tributary area 10 m².
    Calculation path
    1. 1

      qz = 0.613 × 1.0 × 1.0 × 0.85 × 45² = 1,055 N/m².

    2. 2

      External: 1,055 × 0.85 × 0.8 = 717.5 N/m².

    3. 3

      Internal: 1,055 × 0.18 = 189.9 N/m².

    4. 4

      Net windward pressure: 527.5 N/m² (0.528 kPa).

    5. 5

      Force on 10 m²: 5.28 kN.

    Result

    qz 1,055 N/m² · net pressure 0.528 kPa · force 5.28 kN.

    Interpreting the result

    The squared velocity term is why coastal wind maps matter so much: moving from 45 to 55 m/s raises the pressure by half. The internal coefficient is the other surprise — an enclosed building can add or relieve pressure depending on openings, which is why GCpi has a sign.

    Assumptions & limitations

    • Main wind-force-resisting system coefficients.
    • Strength-level pressures to be combined with other load cases.
    • Components and cladding use different coefficients and effective wind areas.

    Frequently asked questions

    Why is Kz higher at the top of a building?

    Wind speed increases with height above ground and with exposure roughness, so the velocity pressure rises.

    Is this for cladding too?

    No. Cladding and components use Chapter 30 coefficients, which are higher and depend on the effective wind area.

    What is GCpi?

    The internal pressure coefficient. Enclosed buildings use ±0.18; partially enclosed buildings use a larger value.

    Methodology last reviewed 2026-10-21. Results are informational and not financial or engineering advice — see our disclaimer.