The engine pressure ratio (EPR) is the total pressure ratio across a jet engine, measured as the ratio of the total pressure at the exit of the propelling nozzle divided by the total pressure at the entry to the compressor.
[1] Jet engines use either EPR or compressor/fan RPM as an indicator of thrust.
[2] When EPR is used, the pressures are measured in front of the compressor and behind the turbine.
The integrated engine pressure ratio (IEPR) is a ratio used on some turbofans to include fan discharge total pressure and compressor inlet total pressure.
[3] The IEPR is an engine indicator system unique to the Rolls-Royce RB211.