AbstractThis paper provides a long overdue update on the global non-revenue water (NRW) estimates, initially published in a World Bank publication more than 10 years ago. The authors use a similar approach based on latest data to estimate the volume of water lost by water utilities around the world. The conclusion of this study is that the 2006 estimates were extremely conservative and that realistic NRW estimates are significantly higher. The global volume of NRW has been estimated to be 346 million cubic metres per day or 126 billion cubic metres per year. Conservatively valued at only USD 0.31 per cubic metre, the cost/value of water lost amounts to USD 39 billion per year. Not only is this an enormous financial concern, but elevated NRW also detracts from water utilities, in a time of increasing scarcity and climate change, from reaching their goals of full service coverage, at a reliable level of service at an affordable price.