How is maximum takeoff thrust expressed in aviation?

Maximum takeoff thrust is commonly expressed using N1 or engine pressure ratio (EPR) because these metrics provide a specific and standardized way to quantify the thrust produced by jet engines during takeoff. N1 refers to the rotational speed of the engine's low-pressure turbine in relation to its design parameters, while EPR measures the pressure difference between the engine's inlet and exhaust, serving as an indicator of thrust output. These parameters are critical for pilots and engineers to determine and manage engine performance accurately during takeoff, ensuring safety and efficiency in flight operations.

Using N1 and EPR as measures allows for more precise calculations relevant to engine operations across different aircraft models and conditions, making it a universally recognized expression of maximum takeoff thrust in aviation.