Calculate your protection time with sunscreen based on SPF and skin type.
SPF 30 protects 30x longer than without protection.
Reapply after swimming, sweating, or every 2 hours.
This tool is most useful for tracking trends rather than obsessing over a single data point. Run the calculation monthly with consistent measurement conditions to see whether your metric is moving in the right direction.
A frequent error is failing to control measurement conditions between calculations. Weight and body circumferences vary significantly throughout the day and with hydration levels. Always measure under the same conditions (same time of day, same equipment) to make comparisons meaningful.
Someone returning from a period of inactivity uses the calculator to establish a baseline health metric before starting a new training programme. Monthly recalculations with consistent measurement conditions create a trackable trend that scale weight alone cannot provide.
Sun Protection Factor: multiplier for how much longer you can stay in the sun.
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