A wind claim on the box: turn mph into knots and a Beaufort force with the Met Office rule

A wind claim is only useful if you can say what it means. Boxes and listings give a number in miles per hour, test write-ups give gusts, and forecasters speak in forces and knots. This sheet shows how to move between them using the one conversion rule on the Met Office Beaufort scale page, read on 6 November 2026, then works two real figures through it. It is general information about reading claims, not a test of any umbrella.

The rule and the table

The Met Office lists the scale in knots and says to convert knots to mph by multiplying by 1.15. To go from a claim in mph to knots, divide by 1.15. The page describes sea conditions, so it names speeds but says nothing about umbrellas; our own extra column gives the mph range using the Met Office’s rule.

Worked example 1: a 75 mph claim

Shed Rain’s Vortex V2 43-inch compact page says the umbrella is wind tunnel-tested and proven to resist winds up to 75 mph without flipping inside-out.

1. 75 divided by 1.15 is about 65 knots.
2. 65 knots is above the 64-knot line, so the claim sits in force 12, the hurricane row.
3. The page does not say whether 75 mph is a steady speed or a gust.

The result is a claim at the very top of the scale, made by the maker in its own tunnel. That is not the same as a field result.

Worked example 2: a 40 mph field note

The Guardian’s umbrella tests (updated 28 October 2026) say gusts only reached about 40 mph while the reviewer tested the Vortex V2, and that the umbrella did not invert.

1. 40 divided by 1.15 is about 35 knots.
2. That falls in force 8, the Met Office’s gale row of 34 to 40 knots.
3. The reviewer gives gusts, not a steady speed, and no tunnel.

A gale-force gust with no inversion is a solid result. It is 35 mph below the claim, and nobody has to choose between the two. They answer different questions.

The three-line check for any claim

Fill these in for any umbrella you are weighing. The questions are ours.

A claim that cannot fill in line 1 or line 2 is a marketing number until someone tests it. A claim that fills them in and still sits in force 12 is worth a closer look at the test method, not a purchase.

Your own conversions

Use the table. A box that says 50 mph is about 43 knots, force 9. One that says 60 mph is about 52 knots, force 10. One that says 30 mph is about 26 knots, force 6. These are examples of the arithmetic, not claims we found on any product. For what force 6 and above mean when you are carrying an umbrella on the street, see our umbrella wind speed chart and the sheet on wind warning colours. For how to judge a review’s method, see how to read an umbrella review.

Where the Haven Umbrella fits

Xzvzx and Calm Eden are commonly owned. Calm Eden’s Haven Umbrella is described as storm-proof, and we have no wind speed figure for it, so there is no number to convert; we would not give it a force. We have no outside test of it to quote either. What the listing does say is concrete: 30 carbon fibre ribs, a fold to 40 cm, a weight near 390 g and a canopy of about 105 cm when open. The Haven Umbrella listing is where to start for the facts above, and our Shed Rain review puts one brand’s claim next to its outside tests. Every order includes a Haven Cover and the Wellness Journal (digital); Buy 2 Get 1 Free adds the UV Charm and the Rain Poncho, and Buy 3 Get 2 Free also adds the Haven SPF 50+ Silk Square Scarf.

Sources: Met Office, Beaufort scale; Shed Rain, Vortex V2 43-inch compact page; the Guardian’s Filter umbrella tests. All read on 6 November 2026.