This work aims to calculate of water requirements for carrot under sprinkler irrigation in sandy loam soil at Selkovo village, Sergiev Posad District, Moscow Region, Russia, situated at 56° 35' N latitude, and 38° 09' E longitude. The average yields were 54 ton/ha for the first season and 58.8 ton/ha for the second season for carrot. The total water requirements were 344 mm (3440 m3/ha) and 338 mm (3380 m3/ha), during two successive seasons respectively. The average of temperature of July 17.8 oC at the average of relative humidity of 61%. The relationships between water requirements (E, mm/day) and deficits relative humidity (ds, mbar) having the following formula: Е = a dsb (1) Where, a, b - empirical coefficients of the regression equation. At using experimental data through the two seasons of carrot. That equal a = 1.06 and b = 0.86 then the relation become (Е = 1.06 ds0.86) and the correlation coefficient was 0.959±0.073. This means that in 91.9% of the water consumption of carrot variations in these conditions due to variations in deficits air humidity. For calculating carrot water requirements under sprinkler irrigation was found as Е = КF KC а dsb considering КF– Coefficient depending on wetting pattern under sprinkler and КC – Crop coefficient. The experimental data for growth seasons during calculation the crop coefficient of carrot through growth season was found as КC = 0.649 + 0.128 tr – 0.011 tr2 considering tr as decade number.