Sunscreen Calculator

How Much Sunscreen Do You Need?

Whether you're heading to the beach, going on a hiking trip, or just spending time outdoors, protecting your skin from UV rays is essential. Our Sunscreen Calculator helps you estimate exactly how much sunscreen you need for your entire trip based on your body size, sun exposure time, and the size of your sunscreen bottle.

The general recommendation is to apply 2 mg of sunscreen per square centimeter of skin. For a full-body application, this works out to about 30 ml (1 fl oz) per session. Most people apply far less than the recommended amount, which significantly reduces the level of protection. Using our calculator ensures you pack enough sunscreen for proper protection throughout your vacation.

How It Works

The calculator uses the Mosteller formula to estimate your body surface area (BSA) from your weight and height. It then calculates the total sunscreen needed based on:

• Body surface area - calculated from your height and weight using the Mosteller formula: BSA (m²) = √(weight(kg) × height(cm) / 3600)
• Clothing coverage - how much of your skin is exposed to the sun
• Sun exposure time - how many days and hours per day you'll be in the sun
• Reapplication frequency - sunscreen should be reapplied every 2 hours for continued protection

How to Use the Calculator

Select whether you're calculating for your full body or just your face. For body calculations, enter your weight and height along with your typical clothing coverage. For face calculations, measure your face width (ear to ear) and face height (hairline to chin) in centimeters. Then enter how many days you'll be in the sun, how many hours per day, and the size of your sunscreen bottle.

Sunscreen Application Tips

• Apply sunscreen 15-30 minutes before going outside to allow it to absorb into the skin
• Use enough sunscreen - about 2 mg per cm² of skin, or roughly 30 ml for a full-body application
• Reapply every 2 hours, or more often if swimming or sweating
• Don't forget often-missed spots: ears, back of neck, tops of feet, and lips
• Use a broad-spectrum sunscreen that protects against both UVA and UVB rays
• Check the expiration date - most sunscreens are effective for up to 3 years

Sunscreen for Different Activities

Different activities require different amounts of sunscreen. Swimming and water sports require water-resistant sunscreen and more frequent reapplication. High-altitude activities like hiking or skiing need extra protection as UV radiation increases with altitude. If you're spending time near water, sand, or snow, UV rays can reflect and increase your exposure, so be extra diligent with application.