How Much Sunscreen Does a Child Need? A Calculator for Ages 7–17

Sunscreen only gives the SPF on its label when enough goes on: 2 mg for every square centimetre of skin, the amount used in testing. Most people use far less. The calculator above gives your child an everyday amount, from India's sunscreen consensus rule of thumb scaled to their size, and the tested minimum it should never drop below.

For most children aged 7 to 17, the everyday amount is about ½ to 2 teaspoons for the face and neck each morning, depending on size, and about 1 to 3 tablespoons for the whole body at the pool or the beach.

How is the amount worked out?

In four steps, using standard medical formulas.

1. Skin area. Body surface area comes from height and weight using the Mosteller formula: the square root of height (cm) × weight (kg) ÷ 3,600, in square metres.
2. Face and neck share. A child's head is a bigger share of the body than an adult's. The Lund and Browder chart, used by doctors to estimate skin area by age, gives half the head as 6½% of the body at age 5, 5½% at 10 and 4½% at 15. We use that half for the face and add 2% for the neck.
3. Minimum. Skin area × 2 mg/cm², the tested amount. For a lotion, 1 g is about 1 mL, and a teaspoon holds about 5 mL.
4. Everyday amount. PRISM-ISF (2025) gives adults a practical rule of 1–2 teaspoons for the face and neck and 2–3 tablespoons for the body. We scale it to your child's skin area compared with an average adult's 1.73 m². It comes out higher than the minimum on purpose: the rules of thumb round up, and more is fine.

As a check, India's sunscreen consensus, PRISM-ISF (2025), says 2 mg/cm² equals about 35 mL for an average adult body of 1.73 m². The same formula gives 34.6 g.

Why does the amount matter so much?

Because protection drops when people apply too little. PRISM-ISF notes that "SPF protection is directly linked to the quantity applied", and that most people apply 0.5 to 1.5 mg/cm² instead of 2, "which greatly reduces effectiveness". That's a quarter to three-quarters of the tested amount.

A higher SPF leaves a little more margin on a rushed school morning, but it doesn't replace using enough. Our guide to SPF 30 vs SPF 50 for kids explains the difference.

How often should kids reapply at school?

At least every 2 hours outdoors, and straight after swimming, sweating or towel drying. The American Academy of Dermatology also advises applying sunscreen before going outside, because it takes about 15 minutes to start protecting.

• Morning: face, ears and neck before leaving home.
• PE, recess or sports day: arms, hands and legs too if they're bare, and reapply if they've been out for 2 hours.
• Swimming class: whole-body amount before, and again after towelling off.

Shade, a cap or hat and sunglasses matter too: PRISM-ISF lists them alongside sunscreen for children, and advises avoiding direct sun between 10 am and 4 pm. Our parent's guide to sunscreen for kids in India covers the rest.

How can you make sure your child uses enough?

Measure it once. Put the calculator's amount on a teaspoon so your child sees how much it is, then show them how to dot it on the forehead, cheeks, nose and chin and spread it out. After a few days, they'll know the amount by eye.

For a younger child, see sunscreen for a 9-year-old. For teens, see sunscreen for teenagers in India.

How ado fits in

ado's mineral SPF 50+ sunscreen comes in a 100 mL tube, and zinc oxide is its only UV filter. It's labelled broad spectrum (UVA/UVB); no PA rating is stated, and it makes no water-resistance claim, so reapply after swimming, sweating or towel drying. It contains fragrance (the last ingredient), so patch-test first if your child has sensitive skin.