Weather converter
UV Index Converter
Erythemal irradiance
200 mW/m²
Risk category
Very high
| Skin type | Description | Est. time to burn |
|---|---|---|
| I | Very fair, always burns | ~17 min |
| II | Fair, burns easily | ~21 min |
| III | Medium, sometimes burns | ~25 min |
| IV | Olive, rarely burns | ~38 min |
| V | Brown, very rarely burns | ~50 min |
| VI | Dark brown or black | ~83 min |
How the uv index converter works
The UV index compresses erythemal irradiance into a simple scale: one UV index point equals 25 mW/m² of sunburn-weighted ultraviolet power. Enter a UV index to see the physical irradiance and an estimated unprotected time-to-burn for each skin type.
1 UVI = 25 mW/m² erythemal irradiance burn time ≈ MED ÷ (1.5 × UVI) minutesQuick tips
- Each UV point = 25 mW/m² of sunburn-weighted radiation reaching the ground.
- From UV 3 upward, protect: SPF 30, hat, and shade at midday.
- Burn times are ceilings, not targets - water, sand, snow and altitude all shorten them.
WHO UV index risk categories
| UV index | Category | Protection needed |
|---|---|---|
| 0-2 | Low | Sunglasses on bright days |
| 3-5 | Moderate | SPF 30, hat, midday shade |
| 6-7 | High | SPF 30+, cover up 10am-4pm |
| 8-10 | Very high | SPF 50, minimize midday sun |
| 11+ | Extreme | Avoid midday sun entirely |
Frequently asked questions
What does one point of UV index equal physically?
25 milliwatts per square meter of erythemally-weighted (sunburn-effective) UV irradiance. UV index 8 means 200 mW/m² is reaching the ground.
How accurate are time-to-burn estimates?
They are rough guides based on the minimal erythemal dose (MED) for each skin type under the standard weighting. Reflection, altitude, medication and prior tanning all shift the real number - treat them as ceilings, not targets.
Does a higher UV index mean it feels hotter?
No. UV is invisible and carries little heat - a cool spring day can have a burning UV index of 8 while a scorching evening has UV 0.