Wind Load Calculator (Simplified)
Simplified wind load calculator. Returns wind pressure and total force on a flat surface from wind speed, area and drag coefficient. Educational guideline, not code.
Wind Load Calculator
Enter a gust-level speed. Codes define their design wind differently: a 10-minute mean in the Eurocode, a 3-second gust or an hourly mean in older codes. Typed in as it stands, a mean speed gives a pressure that is too low. Which speed to enter.
Only the raised-sign value comes from a code. The other shapes are indicative figures for comparison, not code coefficients.
Please tick the acknowledgement above before calculating.
How to use the wind load calculator
Enter the wind speed
Type a gust-level wind speed and choose mph, km/h or m/s. A 10-minute or hourly mean cannot simply be scaled up to a gust: use the design wind your code defines, with that code's own factors. Typed in as it stands, a mean speed gives too low a pressure. Wind load grows with the square of speed, so the speed dominates the result.
Enter the surface area
Use the area of the surface facing the wind, in square feet or square metres — the projected (frontal) area perpendicular to the wind.
Pick a drag coefficient
Cd captures the shape. The default, 1.8, is the force coefficient EN 1991-1-4 gives a signboard raised above the ground (§7.4.3). The other presets are indicative figures for comparing shapes, not code values.
Acknowledge, then read force and pressure
You get the total force, the pressure times Cd and the dynamic pressure q, in US and SI units. This is a simplified estimate, not a code wind-load calculation; a real design follows the governing wind code.
Wind load — why speed matters more than anything
The square law that defines the problem
Wind exerts force on anything in its path, and for signs, fences, solar panels, billboards and building faces that force decides whether the structure stands or blows over. The starting point is the dynamic pressure of moving air, q = ½ρV², which depends on the air density ρ and the square of the wind speed. With ρ = 1.226 kg/m³, q is 0.613 times the speed squared when the speed is in metres per second and q is in pascals, or 0.00256 times the speed squared when the speed is in miles per hour and q is in pounds per square foot. The codes' own densities sit within about 2% of that: EN 1991-1-4 recommends 1.25 kg/m³ and Hong Kong's 2019 Code takes 1.2 kg/m³. The total force on a surface is then this pressure times a shape factor — the drag or force coefficient, Cd — times the area facing the wind: F = q × Cd × A. The Eurocode, EN 1991-1-4, gives a signboard raised above the ground a force coefficient of 1.80 (§7.4.3), and that is the calculator's default; a National Annex can set its own figures for some coefficients, so the annex for your site has the last word. Its other presets are indicative figures for comparing shapes; a smooth cylinder takes a much lower value than a flat surface because the air slides around it.
The defining feature is the square law. Because pressure scales with the square of speed, wind force is extraordinarily sensitive to it: a wind 40% stronger nearly doubles the load, and a doubling of speed quadruples it. This is why a structure comfortable in everyday breezes can be destroyed in a storm, and why the codes define their design wind speed so carefully, by return period and by averaging time. Area and shape matter, but speed is the lever that swings the result the most.
"Wind load follows a square law: double the wind speed and the force quadruples. A structure that shrugs off a breeze can be torn apart by a gust — which is why the design wind speed is everything."
Which wind speed to enter
The formula cannot tell what kind of speed it is given, and the codes do not all mean the same thing by a design wind speed. EN 1991-1-4 (§4.2) defines its basic wind velocity as "the characteristic 10 minutes mean wind velocity" at 10 m above open country, with a 50-year mean return period (§3.4). In Singapore, the Land Transport Authority's Standard Details of Road Elements (Revision I, in force from 1 June 2026) set 22 m/s as the characteristic 10-minute mean wind velocity for the structures they cover, with the wind actions derived from SS EN 1991-1-4 and its Singapore National Annex. Hong Kong's Code of Practice on Wind Effects 2019 gives no speed to type at all: it publishes a table of reference pressures, 1.98 kPa at 10 m for example.
Older Singapore practice shows how far apart the bases can sit. BCA's Approved Document of September 2019 listed 33 m/s as a "3 second gust speed" for the British CP 3 route and 22 m/s as an "hourly mean speed" for BS 6399. Since its March 2025 revision, which applies to plans first submitted from 1 September 2025, the Approved Document requires Eurocode design and calls those British standards superseded. Typed into this calculator as they stand, the two old figures give 668 Pa for 33 m/s and 297 Pa for 22 m/s, 2.25 times apart. That ratio is only what ½ρV² does with two raw numbers: each code then applied its own factors, so the two routes never produced design pressures that far apart.
The formula returns the pressure of whatever speed it is handed, so a mean speed gives a mean pressure, and the peak load a gust delivers is higher. A mean speed cannot simply be multiplied up by one fixed gust factor. The codes build the peak into their own rules: the Eurocode's recommended rule for the peak velocity pressure is (1 + 7·Iv)·½ρvm², where Iv is the turbulence intensity at the height concerned, and Singapore's National Annex is among those allowed to set its own. Those rules depend on terrain, height and the code. So this page offers no conversion: use the design wind your governing code defines, with that code's own factors, and read a figure from this calculator as the raw ½ρV² of the speed you typed. With this calculator's air density, matching Hong Kong's 1.98 kPa takes a speed of about 56.8 m/s.
A guideline, not a code calculation
The formula here is genuinely useful for understanding wind force and for rough comparisons — sizing the footing of a sign, sensing how a panel will load its supports, appreciating the effect of a higher design speed. But it is deliberately simplified and must not be mistaken for a real wind-load design. Wind codes — EN 1991-1-4 (adopted in Singapore as SS EN 1991-1-4 with a National Annex), Hong Kong's Code of Practice on Wind Effects 2019, Malaysia's MS 1553 and ASCE 7 in the United States among them — wrap this basic physics in a great deal more: gust and turbulence terms, terrain and exposure, height and topography, directionality, internal and external pressure coefficients that differ across a building's faces and roof, and factors for the consequences of failure. They also set their own design wind for each place, tied to a return period, rather than a single number. Some rules sit outside any formula: Singapore's National Annex says the Eurocode's terrain categories do not apply in Singapore, and that every building should be able to resist, as a minimum, a design horizontal load equal to 1.5% of its characteristic dead weight. Ignoring all this can under- or over-estimate the real load substantially. Treat this calculator as an educational estimate of the basic wind force; any structure that must resist wind — a sign, canopy, solar array or building element — has to be designed by a licensed engineer to the governing code, and never on the basis of this simplified figure alone.
Pressure scales with the square of the wind speed
Force = q × Cd × A (pressure × shape × area).
q = 0.613·V² (Pa, m/s) = 0.00256·V² (psf, mph).
Wind load follows a square law in speed.
Double the speed → 4× the force.
A raised signboard: cf = 1.80 in EN 1991-1-4 §7.4.3.
Use the projected area facing the wind.
Codes add gust, exposure and height factors.
Hong Kong's 2019 Code publishes pressures, not speeds.
Design winds differ by averaging time and return period: 3-s gust, 10-min mean, hourly mean.
Curved shapes shed wind — lower Cd than flat ones.
Frequently asked questions
In simplified form, the wind force on a surface is F = q × Cd × A, where q is the dynamic pressure of the wind, Cd is a drag/force coefficient for the shape, and A is the area facing the wind. The dynamic pressure is q = 0.613 × V² in pascals (V in m/s), or 0.00256 × V² in pounds per square foot (V in mph). For a peak load, V has to be a gust-level speed; a 10-minute or hourly mean gives a lower, mean pressure. The calculator computes both the pressure and the total force in US and SI units.
Because the pressure depends on the square of the speed. A 40% increase in wind speed nearly doubles the load, and doubling the speed quadruples it. This square law is why structures that are perfectly stable in ordinary winds can fail in storms, and why the design wind speed — including what kind of speed it is, a gust or a mean — is the single most important input. Area and shape matter, but speed dominates.
The drag or force coefficient, Cd, captures how a shape interacts with the wind. The Eurocode, EN 1991-1-4, gives a force coefficient of 1.80 for a signboard separated from the ground by more than a quarter of its own height (§7.4.3, which also applies it lower down when the sign is no wider than it is tall); that is the calculator's default. A National Annex can set its own figures for some coefficients, so check the one that applies to your site. The other presets — a free-standing flat plate, a wall at ground level, a building face, a pitched roof, a pole — are indicative figures for comparing shapes, not code coefficients. The pitched-roof figure is the roughest of these: a real roof sees suction and pressures that vary across its surface (see the uplift question below). Choosing the right coefficient matters — a flat-surface value used for a pole would badly overestimate the force.
No. This is a simplified physics estimate. Code methods — EN 1991-1-4 and Singapore's SS EN 1991-1-4 with its National Annex, Hong Kong's Code of Practice on Wind Effects 2019, Malaysia's MS 1553, ASCE 7 in the United States — add gust and turbulence terms, terrain and exposure, height and topography, directionality, internal and external pressure coefficients and factors for the consequences of failure, and each sets its own design wind. Those refinements can change the load substantially. This tool is for understanding and rough comparison only, never for permit submissions or structural design.
For a real design, the wind comes from the code that governs your site, and the codes define it differently, by averaging time as well as return period. EN 1991-1-4 uses a 10-minute mean at 10 m with a 50-year return period. In Singapore, BCA's Approved Document requires Eurocode design (SS EN 1991-1-4 with the Singapore National Annex) for plans first submitted from 1 September 2025, and LTA's road-element standards (Revision I, in force from 1 June 2026) set 22 m/s as a 10-minute mean. The Approved Document of September 2019 had also listed 33 m/s as a 3-second gust (CP 3) and 22 m/s as an hourly mean (BS 6399), routes it now calls superseded. Hong Kong's 2019 Code publishes reference pressures rather than speeds. For Malaysia's MS 1553:2002, Nizamani and colleagues (2018) report the basic wind speed as a 3-second gust at 10 m. A mean speed cannot simply be scaled up to a gust: use the design wind your code defines, with that code's own factors. Typed in here as it stands, a mean speed understates the pressure. For this educational tool you can enter any speed up to 120 m/s to see its effect, but choosing the correct design wind is part of a real assessment and is specific to the site.
No. This tool gives a single force on a surface perpendicular to the wind. Real wind behaviour is more complex: wind flowing over a roof creates suction (uplift), corners and edges see local pressure peaks, and a building has different pressures on its windward, leeward, and side faces. These directional and uplift effects are exactly what the code pressure coefficients handle and what this simplified calculator does not. Roof and cladding design must use the code method.
Use the projected (frontal) area presented to the wind — the area of the surface as seen looking along the wind direction. For a flat sign facing the wind, that's simply its height times width. For an angled surface, the projected area is smaller than the actual surface area. The calculator multiplies your area by the pressure and drag coefficient, so entering the correct frontal area is important for a meaningful estimate.
No. Use it to learn how wind force scales and for rough comparisons only. Any structure that must resist wind — a sign, canopy, solar array, fence, or building element — must be designed by a licensed engineer to the governing wind code, which accounts for the many factors this simplified formula omits. Relying on this estimate for a real design could badly under-estimate the load and is unsafe.
You can use it to get a feel for the wind force on any flat element — a fence panel, a ground-mounted solar array, a billboard or sign — by entering its frontal area, a suitable drag coefficient, and a wind speed. That's helpful for understanding the loads and roughly sizing supports or footings. But these structures still need a proper code-based wind design: solar arrays and signs in particular have specific code provisions and can experience significant uplift and overturning that this simplified force does not capture.
No. The values you enter are processed entirely in your browser. Nothing is sent to a server, stored, or shared, and no account is required. The calculation runs on your device only.
Method & sources
How it computes
Dynamic pressure q = 0.613·V² (Pa, V in m/s), which is ½ρV² at ρ = 1.226 kg/m³ and equals 0.00256·V² psf with V in mph; force F = q·Cd·A on the projected area. Default Cd 1.80, the EN 1991-1-4 §7.4.3 signboard force coefficient; other presets are indicative. V must be a gust-level speed: a 10-minute or hourly mean understates the pressure. Speeds over 120 m/s are refused. No height, terrain or gust factors; not a code design calculation.
What this tool implements
- q = ½ρV² with ρ = 1.226 kg/m³ (0.613 = ½ × 1.226). The psf figure is the same value converted (0.613 × 0.44704² ÷ 47.88 = 0.00256 psf per mph²), so the two units cannot disagree. Code densities sit within about 2% of it: EN 1991-1-4 §4.5 Note 2 recommends 1.25 kg/m³; Hong Kong's Code of Practice on Wind Effects 2019 takes 1.2 kg/m³.
- The speed entered is used as given, and the codes define the basic wind differently. EN 1991-1-4 §4.2(1)P: "the characteristic 10 minutes mean wind velocity" at 10 m in open country, with a 50-year mean return period (§3.4(1)). LTA Standard Details of Road Elements, Revision I (in force from 1 June 2026), General Note 5: 22 m/s as the characteristic 10-minute mean, actions from SS EN 1991-1-4 and its Singapore National Annex. Hong Kong 2019: a reference-pressure table (Table 3-1, 1.98 kPa at 10 m). History, not current practice: BCA's Approved Document of September 2019 listed 33 m/s as the "3 second gust speed" for CP 3 Chapter V Part 2 and 22 m/s as the "hourly mean speed" for BS 6399 Part 2; from 1 September 2025 (circular APPBCA-2025-03) it requires Eurocode design and calls those standards superseded. A mean speed cannot simply be scaled up by one gust factor; the page tells the reader to use the design wind their code defines, with that code's own factors, and offers no conversion.
- Default shape coefficient: EN 1991-1-4 §7.4.3(1), Expression (7.7), cf = 1,80 for a signboard separated from the ground by more than h/4 (and also below h/4 when b/h ≤ 1) — the Eurocode's value; the page tells the reader that a National Annex can set its own figures for some coefficients. The other presets (wall at ground level 1.3, free-standing plate 2.0, building face 1.2, pitched roof 0.8, pole 0.5) are indicative figures with no code source, labelled as such on the page.
- Deliberately omitted: height (exposure) and terrain factors, topography, directionality, the gust or turbulence term that turns a mean into a peak (the Eurocode's recommended rule, Expression (4.8): qp = [1 + 7·Iv]·½·ρ·vm², which Singapore's National Annex lists among the parameters it may set), internal pressure and the code pressure coefficients. Singapore's National Annex adds that the EN terrain categories do not apply in Singapore, and that every building should resist at least a design horizontal load of 1.5% of its characteristic dead weight.
- RECATOOLS conventions: speeds above 120 m/s (432 km/h, about 268 mph) are refused as a sanity limit, not a code or physical value; non-positive speed or area is refused; results below 100 are shown to three significant figures so a small load never prints as 0.
Sources
- CEN. EN 1991-1-4:2005+A1:2010. Eurocode 1: Actions on structures — Part 1-4: General actions — Wind actions. Brussels: European Committee for Standardization; 2010. §3.4(1), §4.2(1)P, §4.5 Note 2, Expression (4.8), §7.4.3(1). https://eurocodes.jrc.ec.europa.eu/EN-Eurocodes/eurocode-1-action…
- SPRING Singapore. Singapore National Annex to SS EN 1991-1-4:2009, Eurocode 1: Actions on structures — Part 1-4: General actions — Wind actions. Singapore: SPRING Singapore; 2009. National Foreword (free preview).
- Building and Construction Authority. Approved Document, Version 7.02A. Singapore: BCA; September 2019. B.3.2.1(c) Wind loads (superseded for plans first submitted from 1 September 2025). https://www.bca.gov.sg/publications/BuildingControlAct/others/App…
- Building and Construction Authority. Circular APPBCA-2025-03: Updates to the Approved Document (1 March 2025). Singapore: BCA; 3 March 2025. Removes the old BS/SS references; B.3.1a requires Eurocode design for plans first submitted on or after 1 September 2025.
- Land Transport Authority. Standard Details of Road Elements, Revision I. Singapore: LTA; March 2026 (in force from 1 June 2026). General Note 5, characteristic 10-minute mean wind velocity 22 m/s. https://www.lta.gov.sg/content/dam/ltagov/industry_innovations/in…
- Buildings Department. Code of Practice on Wind Effects in Hong Kong 2019 (amended December 2023). Hong Kong: Buildings Department; 2019. Table 3-1 and Eq 6-2; air density 1.2 kg/m³. https://www.bd.gov.hk/doc/en/resources/codes-and-references/code-…
- Nizamani Z, et al. Wind load effects on high rise buildings in Peninsular Malaysia. IOP Conf Ser: Earth Environ Sci 2018;140:012125. Reports MS 1553:2002's basic wind speed as a 3-second gust at 10 m (secondary source; the standard itself was not opened). https://doi.org/10.1088/1755-1315/140/1/012125
What can make this go out of date
- EN 1991-1-4 second generation: the Swedish Institute for Standards lists SS-EN 1991-1-4:2026, edition 2, approved 25 March 2026. Whether and when Singapore adopts the new edition is not known.
- LTA has published Revision J of the Standard Details of Road Elements, taking effect from 1 March 2027; General Note 5 (22 m/s, 10-minute mean) is unchanged in it. The current BCA Approved Document PDF (after the March and October 2025 updates) was not opened; its Eurocode requirement is taken from circular APPBCA-2025-03.
Pick up where you left off
Stored only in this browser — never sent to our servers.