Created by Gabriela Diaz
Last updated: Aug 06, 2022

Use the wind load calculator to determine the force that wind exerts over a structure. By simply entering some of the most important parameters involved in this calculation, this tool will instantly estimate the dynamic pressure and load.

If you're interested in learning more about this topic, we've created an accompanying text where we discuss:

• What wind force is;
• The different types of wind loads, including the uplift wind load on roofs;
• The factors that generate wind load;
• How to calculate wind pressure from wind speed; and
• How to calculate the lateral wind force.

Let's go! 🌬

Different types of loads are considered in the design and construction of new structures and in evaluating existing ones. As one can imagine, one of the goals when designing a building, house, or any structure is that it can withstand different types of loads without experiencing any damage. Below are some of the typical kinds of loads that are exerted over a structure:

• Sustained loads — as is the case of the structure's weight.
• Live loads — which correspond to the weight of the furniture, residents, or any other movable or temporary weight, e.g., people coming in and out of the building or moving from one room to another.
• Environmental loads — such as earthquakes, snow, and the wind.

In recent decades, wind load has become more critical in the design of buildings and structures as the tendency to work with lighter materials has increased. Wind load is the type of load we'll be discussing in the following sections.

In simple terms, wind load is the force or pressure that wind exerts on the outside of a structure. Air carries energy as it moves freely through space, and when it encounters a barrier, such as a wall, this energy is suddenly applied against its surface in the form of force or pressure (force per unit of area).

There are three types of wind loads:

• Uplift load — this wind load on roofs generates a lifting effect. Air entering through windows or other openings can flow beneath the roof and push it upwards.
• Shear load — this one refers to the horizontal pressure that could tilt a building.
• Lateral load — this is also a horizontal pressure with a pushing effect that could move a structure off its foundations.

The following are the key elements that influence lateral wind load:

• Wind speed — winds at higher speeds generate greater loads.

• Density of the air — as a general practice, the air density is taken as 1.225 kg/m3 / 0.0765 psi, which corresponds to a temperature of 15°C / 59°F and sea level altitude. For conditions significantly different than these, it is better to use the local density value to get more accurate results.

You can use the air density calculator to determine air's density at other conditions🌬

• Impact angle — the angle at which the wind hits the structure, measured from the horizontal. For instance, a wind hitting at 90° generates greater loads than the same wind at 45°.

• Shape of the structure — this refers to properties such as the structure's height, width, and geometry. For example, taller buildings are subjected to greater wind loads than shorter ones.

## How to calculate the wind load — Calculate wind pressure from speed

The wind load formula employed by the wind load calculator is a simplified version that allows getting a first estimate of the value of a lateral wind load. This is the formula:

\small \begin{aligned} F &= q_s \times A_e \\ F &= q_s \cdot A \cdot sin(\alpha) \end{aligned}

where:

• $F$ — Wind load or wind force, usually in N or kN;
• $q_s$ — Dynamic pressure;
• $A_e$ — Effective surface area;
• $A$ — Total area; and
• $\alpha$ — Angle between the horizon and the surface.

To calculate the dynamic pressure $q_s$, we use the following expression:

$\small q_s = \cfrac{\rho \ V^2}{2}$

where:

• $q_s$ — Dynamic pressure in Pa;
• $\rho$ — Wind's density at the conditions of site, usually 1.225 kg/m3 / 0.0765 psi is used (15°C / 59°F at sea level); and
• $V$ — Speed of the wind in m/s. You can learn more about other speed units with the speed converter.

With this formula is possible to calculate pressure from wind speed.

As we mentioned, these expressions are used for quick calculations. However, suppose you would like to perform a more in-depth calculation. In that case, you should use the formulae and methodology established in the proper codes and standards, which consider many other factors.

🙋 We have a dedicated pressure calculator where you can learn what pressure is and how to calculate it!

## Using the wind load calculator

Let us see how to use the wind load calculator to find the wind force on a structure:

1. To start, input the Wind Velocity and Air Density.

The calculator is set to a default wind density value for 15°C (66°F) and at level sea, which can provide a reasonable estimate if you don't know the actual wind density of your problem. However, you can change it to a custom one that adapts to your wind's characteristics.

2. In the section below, The loaded object, enter the related values to the structure: Surface area and Surface angle. This angle is between the horizon and the structure.

3. With this information, the calculator will determine the Dynamic pressure and the Wind load.

🙋 Calculating stress and strain is very important when designing any structure. You can learn how to calculate these with the stress calculator.

Gabriela Diaz
The environment
Wind velocity
mph
Air density
lb/cu ft
The default air density is for 15°C/59°F at sea level. If you need to change this value, check our air density calculator.
Surface area
ft²
Surface angle
deg
Dynamic pressure
psi
N
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