Water requirement in a cropped field can be measured directly with tensiometers or neutron probe method or it can be estimated from meteorological data by means of empirical formulae. A field experiment was carried out at the University of Port Harcourt to determine the pattern of water used by maize crop during the growth period, calculated by the Blaney-Criddle and Standard Class A Pan Evaporation data. Results showed that total crop water requirement during the growing season was 456.9 mm, with mean daily consumptive used rate of 4.22 mm and 3.91 mm using the Blaney-Criddle and Pan Evaporation data. Peak period of water used by the crop was found at tasseling (5.66 mm day^-1), and during yield formation period (6.31 mm day^-1), calculated with the Blaney-Criddle, 5.03 mm day^-1 and 4.78 mm day^-1 respectively with pan evaporation data. The functional model: Y = 12.04 + 1.617x, R² = 0.604 for leaf area index (LAI) and Y = 22.01 + 0.914x, R² = 0.620 for plant height can be used to predict water used by the plant. Sand content tended to increase the amount of water used by the plant while clay content showed non-significant negative effect on water used by the crop. Therefore, both the Blaney-Criddle and Pan Evaporation formulae can be used to estimate the amount of water used by the crop in the study area and similar areas in the humid tropics.