Beach gear by the numbers
For a day at the beach you need four things sized correctly: shade that fits your group, an anchor and ballast that match your sand, sun protection matched to hours in the water, and swim gear fitted to your foot and the water temperature. A 2.4 m umbrella shades four people, SPF 30 filters about 97% of UVB, and 2 mm of wetsuit foam is enough above 24 °C — the rest of this guide is the numbers behind those choices.
| Item | Specification | Coverage or use case |
|---|---|---|
| Beach umbrella, 1.8 m (6 ft) | Round canopy | Shades about 2.5 m² of sand; seats 2 people |
| Beach umbrella, 2.4 m (8 ft) | Round canopy | Shades about 4.5 m² of sand; seats 4 people |
| Sand anchor pole, firm packed sand | 1.5–2.0 m long | Holds where the ground is dense |
| Sand anchor pole, soft dry sand | 0.5–0.9 m long | Shorter pole resists levering out of loose grains |
| Sand anchor pole, saturated wet sand | 30 cm or less | Longer poles start to tip the umbrella |
| Ballast weight | 4–30 kg per anchor | 2.4 m umbrella in a 10 km/h onshore wind: roughly 15–20 kg |
| Wetsuit, water above 24 °C | 2 mm foam | Light insulation for warm water |
| Wetsuit, water below 18 °C | 5 mm foam | Extra foam also adds buoyancy |
Four categories cover the day: shade, sun protection, swim gear and, for children, a rated life jacket.
Shade means an umbrella or a pop-up shelter sized to the group. A 1.8 m round umbrella covers about 2.5 m² of sand and seats two people; a 2.4 m canopy covers about 4.5 m² and seats four. Pop-up shelters span 2 × 2 m to 3 × 3 m of ground, and the largest dome only holds if each of its four corners is staked and the tray carries ballast.
Sun protection is a sunscreen and a UPF-rated shirt chosen by hours, not by the biggest number on the shelf. SPF 15 already filters about 93% of UVB; SPF 30 about 97%; SPF 50 about 98%. Whatever the rating, the coating must be renewed every 2 hours of swimming or heavy sweating.
Swim gear is fins, a wetsuit and goggles fitted to the body and the water. Fins run 2–5 cm shorter than the foot, wetsuit foam follows the water temperature in three bands, and goggle tint follows the light. Children between 14 and 41 kg need a life jacket matched to body weight, with buoyancy ratings from 3.4 to 15.9 kg.
Match canopy size to the group, pole length to the sand, and ballast to the wind.
Start with the canopy. Two people fit under a 1.8 m (6 ft) umbrella with about 2.5 m² of shade; four people need the 2.4 m (8 ft) canopy and its 4.5 m² of cover. Bigger is not automatically better: every extra metre of canopy is extra leverage on the anchor.
The anchor pole length depends on the sand under your feet. Firm packed sand holds poles of 1.5–2.0 m. Soft dry sand calls for a shorter pole, 0.5–0.9 m, because loose grains give the wind a lever. In saturated wet sand at the waterline, anything over about 30 cm starts to tip the umbrella.
Ballast finishes the job. Weights are sold from 4 kg to 30 kg per anchor, and a 2.4 m umbrella standing in a 10 km/h onshore wind needs roughly 15–20 kg. If the canopy shudders and the pole walks sideways, the ballast — not the umbrella — is the part to fix. The full sizing walkthrough is on the umbrella and anchor page.
SPF 30 or 50 plus a UPF 50+ shirt covers long water days — if you keep the two-hour reapplication interval.
The SPF scale flattens quickly. SPF 15 filters about 93% of UVB, SPF 30 about 97% and SPF 50 about 98% — the jump from 30 to 50 buys a single percentage point. For most beach days the practical choice is SPF 30–50 applied generously and renewed every 2 hours of swimming or heavy sweating.
Fabric ratings run on a parallel scale. UPF 15 blocks about 87% of UV, UPF 30 about 94%, and UPF 50+ blocks at least 98%. A UPF 50+ shirt is the closest thing to a set-and-forget layer for someone in and out of the water all day.
The common failure is not a weak product but a stale one: morning sunscreen still on the skin at midday. Set the reapplication clock from the first swim, not from breakfast. The SPF and UPF page breaks the percentages down by time in the sun.
The only scheduled maintenance a beach day needs is sunscreen every 2 hours of swimming or heavy sweating.
Each card names a failure and the measurement that prevents it.
The figures cited throughout are the standard published specification values for each gear category, listed in full in the sections above.