What is the best UV index for tanning?

The best UV index for tanning, in one line

There is no magic number. Tanning starts at about UV 3. Above that, a higher UV index works faster, but it also burns faster. The tan you get from the same dose is the same. Only the clock changes.

For most people, especially beginners, UV 3 to 5 is the easiest range. Sessions are longer, so a minute or two of delay is not a disaster.

What the UV index actually measures

The UV index is a scale for how strongly the sun can burn skin. It was set up by the World Health Organization (WHO) and partners. Each step is a fixed amount of burning UV: UV 1 = 25 mW/m².

The WHO groups it like this:

• 0–2: low
• 3–5: moderate
• 6–7: high
• 8–10: very high
• 11+: extreme

Because the scale is linear, double the UV means the same dose in half the time. The same session at UV 6 takes about half as long as at UV 3.

Why below UV 3 does almost nothing

Below UV 3 there is essentially no tanning response. You can lie out for hours and get little colour, while still adding to long-term skin damage. After sunset there is no tanning at all. The Suntan Workout app simply tells you it is not worth it and to wait.

Why a higher UV index is not better

Many people assume a strong sun gives a deeper tan. It does not. Your skin responds to the dose, and a dose is strength × time. At a higher UV you just reach the same dose sooner, and you reach your burn point sooner too.

Look at Fair skin (type II) at three levels:

UV index	Burns after	First session
4	~40 min	8:00
7	~23 min	4:34
10	~16 min	3:12

At UV 10 the first session is just over three minutes. Miss a turn, fall asleep or chat too long, and you have gone well past it. Pushing beyond your threshold does not make you darker faster. It burns and then peels.

What changes at each level

UV 3–5: moderate

The best UV index for tanning if you are new or fair. Sessions are long enough to plan calmly. In mid-latitudes you often meet UV 3–5 in spring and autumn, or in summer mornings and late afternoons. See how long to tan at UV 4.

UV 6–7: high

A typical summer midday in mid-latitudes. Burn times for Very Fair and Fair skin fall to about 19–27 minutes. Turning over on time now matters a lot. See UV 6.

UV 8–10: very high

Common in southern summers and on holiday beaches. Even Medium skin burns in under half an hour. Sessions get very short, so a timer is essential.

UV 11 and above: extreme

Tropics, high altitude, or noon in a southern summer. Very Fair skin starts to burn after ~12 minutes. If you tan at all, keep the first sessions very short, or go in the early morning or late afternoon. Read how long to tan at UV 11.

Time of day and season

UV is highest around solar noon, roughly 11:00 to 15:00 in summer. It is also higher in summer, closer to the equator and at altitude. Morning and late afternoon bring lower UV.

That gives you a simple trick. On a very bright day, you do not have to choose between burning and staying in. Choose your hour. An early-morning or late-afternoon session can bring you back into the moderate range.

Clouds, wind and reflections

• Clouds: light cloud can let most UV through. The WHO says up to 80%.
• Broken cloud: the riskiest sky. The forecast looks low, but the sun comes back at full strength between clouds.
• Wind and cool air: they hide the burn. UV does not feel hot. You burn as fast at 18°C as at 38°C at the same UV index.
• Water, sand and snow: they reflect UV back at you. Snow reflects the most. Sitting in the shade on the sand is not full protection.

How to check today’s UV index

Most weather apps show the UV index by hour. Check it before you go out, and check it again at midday.

Suntan Workout reads the live UV index where you are standing. It rechecks every 3 minutes. If the UV rises above the plan, it cuts the rest of your session so your dose stays the same. With patchy cloud, it plans as if the sun were fully out. You can also try the numbers in our UV index tanning calculator.

Lower the risk at any UV index

No UV level is “safe” for tanning. Every exposure raises skin cancer and skin-ageing risk. A careful plan only lowers the chance of a burn. Use sunscreen on your face, lips, ears and tattoos. If you have a photodermatosis, take light-sensitising medication, have had skin cancer or have many moles, talk to a doctor first.

For the full method, read how to tan without burning and how long to tan.