The paper presents simple equations for estimation of water needs of fruit trees for conditions of Poland. These formulas are derived on the base of numerical data provided by many authors. Water needs of fruit trees can be estimated on the base of air temperature according to data and methodology of Drupka, Kemmer and Schulz as well as Press. The method of estimation of fruit tree evapotranspiration with the use of crop coefficients for particular months of the vegetation period (acc. to Doorenbos and Pruitt and acc. to Treder) and reference crop (grass) evapotranspiration on the base of air temperature (acc. to: Treder, Hargreaves in modification of Droogers and Allen, Hargreaves in modification of Bogawski and Bednorz, Blaney-Criddle in modification of Żakowicz) are also presented. The presented formulas can be helpful in estimating the irrigation needs of orchards (and vineyards) in conditions of Poland. The presented formulas can be also useful in making decisions on the location of irrigation equipment and the possible application of irrigation in orchards (and vineyards) in Poland.