T2 quantification with multi-echo spin-echo sequences is often hampered by flip angle inhomogeneities and non-rectangular slice profiles. Here, we present a novel time domain signal equation for multi-echo spin-echo sequences with arbitrary excitation and refocusing flip angles and phases. To evaluate the equation simulations and phantom measurements were compared. Excellent agreement was found for the simulated and measured evolution of the transverse magnetization across the slice profile in a CP and a CPMG sequence. T2 mapping using the proposed signal equation and the incorporation of scanner specific RF pulse shapes will greatly improve T2 quantification accuracy.