You need UV above about 3 to tan
Below a UV index of roughly 3, there's not enough UV to build much of a tan. Above that, your skin starts producing melanin — the pigment that tans you.
So a UV of 0–2 is mostly a no-tan zone; 3 and up is where tanning happens.
Moderate UV (around 3–5) is the sweet spot
For most skin types, a moderate UV index tans steadily with a lower burn risk than peak midday sun. As UV climbs into the high (6–7), very high (8–10), and extreme (11+) ranges, tanning gets faster but burning gets much faster — and burning isn't a tan.
Higher UV means shorter safe sessions and stronger SPF, not a free pass to stay out longer.
Your skin type changes the math
Fair skin (Fitzpatrick I–II) burns at lower UV and should keep sessions short. Deeper skin (IV–VI) tolerates higher UV for longer. The "good" UV for tanning is really "good for your skin."
Sunkind reads the live UV for your location and turns it into a specific window for your type — including how long to stay out and the SPF to wear.
Frequently asked questions
What UV index is good for tanning?
A moderate UV index of about 3–5 tans most skin types well with lower burn risk. You need at least ~3 to tan; very high UV burns faster than it tans.
Can you tan with a UV index of 2?
Barely — below about UV 3 there isn't enough UV to build much of a tan. Wait for UV to climb above 3.
Is UV 7 too high to tan?
UV 7 is "high" — you can tan, but burn risk rises sharply. Keep sessions short, wear SPF, and consider a lower-UV window. Sunkind sizes the session for your skin type.