This paper presents an estimation of leakage power and delay for 1-bit Full Adder (FA)designed which is based on Leakage Control Transistor (LCT) NAND gates as basic building block. The main objective is to design low leakage full adder circuit with the help of low and high threshold transistors. The simulations for the designed circuits performed in cadence virtuoso tool with 45 nm CMOS technology at a supply voltage of 0.9 Volts. Further, analysis of effect of parametric variation on leakage current and propagation delay in CMOS circuits is performed. The saving in leakage power dissipation for LCT NAND_HVT gate is up to 72.33% and 45.64% when compared to basic NAND and LCT NAND gate. Similarly for 1-bit full adder the saving is up to 90.9% and 40.08% when compared to basic NAND FA and LCT NAND.