Calculators take an order of magnitude less power. They are also not running all day. Some back of envelope math tells me that a solar panel the size of my pho

Calculators take an order of magnitude less power. They are also not running all day. Some back of envelope math tells me that a solar panel the size of my phone would roughly take 4-5 days to fully charge the phone. If you are interested, you can buy solar charger phone cases - some even with fold out panels. But even then, it's hard to imagine any real utility from them unless you are actively backbacking.