A link budget is the accounting sheet of an RF link. It sums every gain and loss between the transmitter and the receiver to determine the Maximum Allowable Path Loss (MAPL) — the largest distance-induced attenuation the link can survive while still meeting the target SINR. Once you know MAPL, a propagation model converts it into a cell radius. This calculator implements the textbook 3GPP-style link budget: EIRP minus RX sensitivity minus margins yields MAPL, which is then inverted through the COST-231 Hata urban model to produce a cell radius in kilometres. Tune the defaults to your specific scenario — frequency, bandwidth, required SINR, fade margin, penetration loss — and the numbers update instantly.