In the Ford GT40 name, what measurement does “40” indicate?

In the Ford GT40 name, “40” indicates the car’s approximate height of 40 inches.

The GT40 was developed in the 1960s as Ford’s purpose-built endurance racing car. The number referred to the height of the car measured at the windscreen, a key part of its extremely low aerodynamic profile. “GT” identified the vehicle as a grand touring design, while “40” distinguished its approximate height.

The GT40 became famous after winning the 24 Hours of Le Mans four consecutive times from 1966 through 1969. Its success followed Ford’s decision to compete directly with Ferrari in endurance racing. The name is sometimes mistaken for an engine specification or a production count, but it describes the car’s low body height. Road-going replicas and later Ford GT models use the historic name without sharing every detail of the original racing cars.