IEC 62555:2013 establishes general principles relevant to HITU fields for the use of radiation force balances in which an obstacle (target) intercepts the sound field to be measured; specifies a calorimetric method of determining the total emitted acoustic power of ultrasonic transducers based on the measurement of thermal expansion of a fluid-filled target; specifies requirements related to the statement of electrical power characteristics of ultrasonic transducers; provides guidance related to the avoidance of acoustic cavitation during measurement; provides guidance related to the measurement of HITU transducers of different construction and geometry, including collimated, diverging and convergent transducers, and multi-element transducers; provides guidance on the choice of the most appropriate measurement method; and provides information on assessment of overall measurement uncertainties. This International Standard is applicable to the measurement of ultrasonic power generated by HITU equipment up to 500 W in the frequency range from 0,5 MHz to 5 MHz. HITU equipment may generate convergent, collimated or divergent fields. For frequencies less than 500 kHz, no validations exist and the user should assess the uncertainties of the power measurement and measurement system at the frequencies of operation. This International Standard does not apply to ultrasound equipment used for physiotherapy, for lithotripsy for general pain relief.