For use in on-line power monitoring system, an analytical tilt algorithm has been developed using $P_1$ approximation from the transport equation. In this algorithm, radial variation of tilt and tilt equation are employed in order to calculate power tilt. The radial variation of tilt is independent of core parameter and only dependent on core geometry. This analytical algorithm is consist of arithmetic tilt algorithm and vector tilt algorithm. To calculate power tilt, this algorithm uses the response of four symmetrically located incore detector. This analytical algorithm was applied to KNU-1 from cycle 1 through cycle 4 and KNU-2 cycle 1 and cycle 2 using analytic g factor. The comparison of the analytical tilt with regressional tilt shows a good agreement for all cases studied in this work.