Glass · Standards
EN 16612 explained: glass thickness under wind load
EN 16612 (EN 16612:2019, «Glass in building — Determination of the lateral load resistance of glass panes by calculation») is the European standard for working out whether a glass pane carries a load across its face, such as wind. The glass thickness calculator takes its design strength formula and checks two things on a pane supported on four edges: the bending stress, against that strength, and the deflection, against a limit you choose. This page summarises what the calculator implements; it does not reproduce the standard, which is sold by the national standards bodies. The title of the standard is taken from the catalogue entries below, consulted on 8 November 2026.
What the calculator works out with it
- The bending stress σ at the centre of the pane, against the design strength of that glass for that load duration.
- The deflection w at the centre, against the limit you choose.
- The utilisation, the worse of the two checks, and which one governs.
- The thinnest nominal thickness of the same glass and make-up that passes both.
What it asks for
- The width and height of the pane, in mm or inches.
- Monolithic or laminated (two plies), and the nominal thickness of each ply.
- The type of glass: Annealed float — EN 572; Heat-strengthened — EN 1863; Fully tempered (toughened) — EN 12150.
- The design wind pressure, already factored, in kN/m² or psf: the calculator does not work it out from the location. The wind pressure calculator does, to EN 1991-1-4 or ASCE 7.
- How long the load lasts: a 10-minute wind (kmod 0.74, the default) or a 5-second gust (kmod 1.00), if the standard that applies to you allows it.
- The deflection limit, as a fraction of the short span. The calculator page notes that EN 16612 sets no deflection limit: it is a project or national requirement.
The design strength, in the form of EN 16612
| Glass | 10-minute wind, N/mm² | 5-second gust, N/mm² |
|---|---|---|
| Annealed float — EN 572 | 18.5 | 25.0 |
| Heat-strengthened — EN 1863 | 39.4 | 45.8 |
| Fully tempered (toughened) — EN 12150 | 81.0 | 87.5 |
Design strengths as the calculator computes them, from its own code.
What the site assumes
A rectangular pane simply supported on four edges, linear (small-deflection) plate theory with the classical coefficients α and β interpolated by aspect ratio: σ = β·q·b²/t² and w = α·q·b⁴/D, with E = 70 000 N/mm² and ν = 0.23. Design strength in the form of EN 16612 with kmod = 0.663·t−1/16 (a 10-minute wind, 0.74, by default; a 5-second gust, 1.00, on request), γM;A = 1.8 and γM;v = 1.2. Laminated glass by its effective thickness, with no shear transfer and with full transfer. The input is the factored design pressure. The wind lab is a view of this same engine.
Where the calculator departs from the textbook or where we could not check the standard, it says so:
- The β coefficients are the classical ones for ν = 0.3, while glass is nearer 0.23. Solving the plate with both shows the effect is on stress only — the deflection coefficient of a simply supported plate does not depend on ν — and that it overstates the stress by 5.7 % on a square pane, 2.5 % at 1.5 : 1, 1.2 % at 2 : 1 and nothing from 5 : 1. It errs on the safe side.
- Whether wind counts as a 10-minute load or as a gust for kmod depends on EN 16612 and its national annex, which we have not been able to check. The page opens on 10 minutes (annealed glass 18.54 N/mm²) and offers the 5-second gust (25.00 N/mm²).
An example worked by the calculator
A pane of 1200 × 2200 mm, 10 mm fully tempered, under 1.20 kN/m², a 10-minute wind and a deflection limit of short span / 65:
- aspect ratio r = 1.8333, so α = 0.009453 and β = 0.5762;
- bending stress σ = 9.96 N/mm² against a design strength of 81.0 N/mm²: 12 %;
- deflection w = 3.82 mm against a limit of 18.46 mm: 21 %;
- utilisation 21 %, governed by deflection. The thinnest fully tempered glass that passes is 6 mm; in annealed glass, 8 mm.
Open this example in the calculator. The calculator page works the same pane out by hand, line by line.
What it leaves out
- Four supported edges only: no two- or three-edge support, point fixings or structural silicone.
- A single pane: load sharing between the panes of an insulating unit is not modelled.
- Linear theory: once the deflection passes about half the thickness, membrane action makes the real pane stiffer and less stressed (the page warns).
- It does not compute the wind pressure, and there are no post-breakage, thermal stress, barrier or impact checks.
- It is not ASTM E1300 and it applies no national annex.
The calculator is run against 12 published reference cases, side by side with the published figure and the tolerance we accept, on how we check the calculations.
A pre-dimensioning aid for professionals: not a structural calculation, not signed by an engineer, and no substitute for the standard and the national annex that apply to the project.
Sources
Questions people ask
- What does EN 16612 cover?
- EN 16612:2019, «Glass in building — Determination of the lateral load resistance of glass panes by calculation», is the European standard for working out the resistance of glass panes to loads across their face, such as wind. The site's glass thickness calculator uses its design strength formula and checks bending stress and deflection of a pane supported on four edges.
- Does EN 16612 set a deflection limit?
- No. As the calculator page says, the deflection limit is a project or national requirement; the calculator offers short span / 60, 65, 100 and 175 and shows which check governs.
- What design strength does the calculator give toughened glass?
- 81.0 N/mm² for a 10-minute wind and 87.5 N/mm² for a 5-second gust, in the form of EN 16612; annealed float glass gets 18.5 and 25.0 N/mm².