SellerSum is a suite of 13 free fee and profit calculators for online sellers — eBay, PayPal, Etsy, Stripe, Square, Whatnot, Depop, Poshmark, Mercari — plus a marketplace fee comparison hub and a food-cost calculator. Every rate is sourced from official marketplace fee pages with dates, a changelog tracks every fee change, and free email alerts notify you when fees change. No signup, no paywall.
