# This Sunbathing Calculator Tells You How Long You Can Safely Spend In The Sun

Photographed by Rockie Nolan.
Ever found yourself unexpectedly sunburned after an overcast day out? The sun affects us all differently and there's no hard and fast rule for how long we can safely spend in it.
But now there is a clever way to minimise sunburn risk. A doctor has created an ingenious tool that works out the maximum amount of time you can safely spend in the sun based on your skin type, the SPF of your suncream, the intensity of the sun and other factors.

## How to use it

The Sunbathing Calculator, devised by Małgorzata Koperska, MD, requires you to input five bits of information to work out the maximum amount of time you can spend outside without getting burned and damaging your skin. Those are...
1. The intensity of the sun, from low (winter or very cloudy) to extreme (tropical zone), or you can even add the exact UV index of your location in the tool's advanced mode.
2. Altitude, namely your elevation above sea level, which for most people will be up to 1000m if they're sunbathing on the beach, for instance.
3. Whether or not you're on reflective ground, such as water or snow.
5. The SPF of your sunblock.
You can also use the calculator in reverse to work out the SPF you should be using to best protect your skin. Simply leave the calculator's SPF field empty but input the maximum amount of time you're planning on spending outside.
"Recently, with everyone going on holidays and me giving them tips not to get sunburned, I started to wonder if there's a way to estimate how much of which SPF cream we should put on our skin to minimise the risk of skin cancer," Koperska told Refinery29 UK. "I found out it's a matter of a few easily obtainable numbers and putting them together."
She admitted the calculation "isn't strictly precise" but said it's useful information to have to encourage safer tanning habits.

## How it works

The tool uses an equation to make the calculations. "It's the skin phototype coefficient times the cream's SPF, divided by the current UV Index, altitude coefficient, and reflecting ground coefficient," Koperska said. But you don't have to understand any of that to use the tool.