How to Use Sunscreen Calculator
The Sunscreen Calculator prevents the most common sunscreen mistake: applying too little.
- Choose body part(s) — Face, neck, arms, legs or full body.
- Number of people — Group outings sum quickly.
- Outdoor hours — Used to decide reapply count.
- Toggle swimming/sweating — Tightens reapply interval to 1.5 h.
- Set SPF, PA and skin type — For tailored guidance text.
- Read amount per application, total amount, teaspoons, pumps and reapply interval.
Formula & Theory — Sunscreen Calculator
amountPerApp = area_cm2 × 0.002 g/cm² (≈2 mg/cm²)
applications = ceil(hours / reapplyInterval)
totalAmount = amountPerApp × applications × people
teaspoons = totalAmount / 5 mL (≈5 mL per tsp)
pumps = totalAmount / 1 mL (≈1 mL per pump)| Symbol | Meaning |
|---|---|
| area_cm2 | Approximate surface area for the chosen part |
| reapplyInterval | 2 h normally, 1.5 h with swimming or heavy sweating |
| hours | Total outdoor exposure |
| people | Number of people sharing the bottle |
The Sunscreen Calculator uses simple, well-known references so you can scale a 30 mL travel bottle or a 200 mL family tube confidently.
Use Cases for Sunscreen Calculator
- Beach days — Pack the right size bottle and avoid running out.
- Hiking — Estimate sunscreen for a full day above the tree line.
- Sports practice — Plan reapply during halftime with a known interval.
- Pool parties — Account for swimming-induced reapplications.
- Family travel — Multiply by people and days for trip totals.
- Daily commuters — Confirm a small face-only amount is enough.
The Sunscreen Calculator turns “use enough sunscreen” into a number you can actually meet.