Accurate measurement of fuel volume in aircraft tanks is important. Currently, commercial aircrafts usually determine fuel volume with a sum of one-dimension look-up tables (1D-LUT) or a multi-dimension look-up table (MD-LUT). By introducing an equivalent sensor, a reduced-dimension look-up table (RD-LUT) algorithm has been designed, which improves the table looking-up efficiency and reduces database scale with a premise of certain precision. A database is established with the help of fuel quality simulation platform. Numerical method for least mean square surface fitting (LMSSF) is adopted to fit fuel surface. Then fuel surface angles and equivalent sensor output (fuel height) are calculated. Fuel volume is obtained by looking up pre-established table. Theoretical analyses demonstrate the advantages of RD-LUT compared with typical methods and a simulation example based on actual aircraft wing tank verifies RD-LUT's accuracy.