Sunscreen Calculator
Use dermatologist guidelines (2 mg/cm²) to plan how much SPF you need based on height, weight, coverage, and reapplication habits.
Face + arms ≈ 35%, full body ≈ 90–100%.
Dermatologists recommend every 2 hours, more often if swimming.
Typical travel bottle is 100 ml; full size is 150–200 ml.
Usage Snapshot
Per application
28.7 ml
≈ 0.97 fl oz
Applications per day
3
Daily total: 86 ml
Bottle coverage
1.7 days / bottle
Bring 5 bottle(s) for 7 days
How to Use This Calculator
Estimate body coverage
Full-day beachwear may be 90–100%. Office days might be 30–40% if only face, neck, and arms are exposed.
Factor in reapplication
Sweat, swimming, and UV intensity mean reapplying every 2 hours (or sooner). Adjust the interval to match your routine.
Plan supplies for the trip
Enter your bottle size and number of days. The calculator tells you how many bottles to pack to avoid running out.
Formula
BSA (m²) = √(Height_cm × Weight_kg ÷ 3600)
Sunscreen/Application = BSA × Coverage × 10,000 × 0.002 g
Applications/Day = Ceiling(Hours ÷ Reapply Interval)
Bottles Needed = (Daily Usage × Trip Days) ÷ Bottle Size
Example: 170 cm, 68 kg → BSA ≈ 1.82 m². 80% coverage yields ~29 ml/application. With 3 applications/day, plan for 87 ml/day.
Sun Safety Tips
Sunscreen is just one part of sun protection. Combine it with shade, clothing, and smart timing to lower UV exposure.
- Apply sunscreen 15 minutes before sun exposure for better absorption.
- Use broad-spectrum SPF 30+ for daily wear; SPF 50+ for intense sun.
- Don’t forget ears, scalp, tops of feet, and back of hands.
- Replace bottles yearly—formulas can degrade with heat and time.
Frequently Asked Questions
Is SPF different from amount applied?
The SPF rating assumes you applied the recommended quantity. Using less drastically reduces protection, so follow the measured amounts.
How do I adjust for kids?
Enter height and weight for each child or use average pediatric measurements. Kids often need similar amounts as adults by age 10.
Does spray sunscreen change usage?
Sprays still require 2 mg/cm². Spray in sections until skin glistens and rub in to ensure even coverage.
What if I wear UV protective clothing?
Reduce the coverage percentage to reflect the skin still exposed (e.g., face, hands). Protective clothing reduces the amount required.