Abstract: An apparatus and method for measuring the length of a tubular body. The apparatus comprises: a transmitter (10) positioned at first end of the tubular body (12) for transmitting an acoustical signal along the interior of the body (12), a reflecting medium (14) provided at the other end of the body (12) for reflecting the transmitted acoustical signal, acoustical receivers (26, 28) for measuring the period of time for the signal to be transmitted along the body (12) from the transmitter (10) to the second end of the body (12) and be reflected back to the first end, acoustical receivers (26, 28) provided along the central axis of the body (12) for measuring the speed of sound therein, and, circuitry (42, 44) for calculating and displaying the length of the body (12) as a function of the period of time and speed of sound in the body (12).