This International Standard 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; 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.