How to use the time to sunburn calculator
Estimate how many minutes you can stay in the sun before skin starts to burn, from UV index and sunscreen SPF. Enter minimal erythema dose, sunscreen spf, uv index in the fields above; the time to start burning are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “how long before sunburn”, “sun exposure time”, “SPF burn time”, “calculate time to sunburn”, “find time to start burning”.
Formula
Variables
- med — Minimal erythema dose (J/m²)
- spf — Sunscreen SPF
- uvi — UV index (index)
Worked example
With minimal erythema dose = 200 J/m², sunscreen spf = 15, uv index = 8 index, the calculator gives time to start burning ≈ 250 minutes; time to start burning ≈ 4.166667 hours.
Frequently asked questions
What is the time to sunburn calculator used for?
Estimate how many minutes you can stay in the sun before skin starts to burn, from UV index and sunscreen SPF. It helps with questions such as “how long before sunburn”, “sun exposure time”, “SPF burn time”.
What is the formula for the time to sunburn calculation?
Time to start burning (minutes) = med × spf / (uvi × 0.025) / 60. Time to start burning (hours) = [Time to start burning] / 60. Here med is minimal erythema dose (J/m²), spf is sunscreen spf, uvi is uv index (index).
What inputs do I need for the time to sunburn calculator?
You need minimal erythema dose in J/m², sunscreen spf, uv index in index. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the time to sunburn calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the time to sunburn result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.