NHS hospitals could carry out 280,000 more non-emergency operations a year by organising operating theatre schedules better, a new study suggests.
The research, which looked at data from 2016, found more than two hours were wasted each day on the average operating list.
The study says avoidable factors like late starts led to the loss of time.
The analysis, seen by the BBC ahead of publication, looked at theatres in 100 NHS Trusts in England.
A total of 1.64 million routine surgical procedures were carried out in 2016, including eye, ear, nose and throat operations and orthopaedic procedures.
Routine operations are considered non-emergency, and each surgical team will have a daily operating theatre list of patients who are scheduled to go under the knife.
Waiting times for routine operations are going up and there is an ongoing debate over whether more money is needed for the NHS or whether it could be more efficient.
The report, by regulator NHS Improvement, says it is not a question of getting surgeons to work harder.