FlightRefundCalc is a free educational calculator for flight delay, cancellation, and denied-boarding rights under EU261, UK261, and U.S. DOT rules. Enter the itinerary. See which framework applies and a preliminary compensation band. Then write to the airline with a printable letter instead of handing 35–50% to a claim company. No signup. No boarding-pass upload. Not a law firm. Not a payout guarantee. Optional AirHelp referral is disclosed if you still want someone else to file.