A hazard ratio presents one benefit of exercise as reducing annual mortality risk by 19%. Alternatively, speed-of-ageing metaphors present this as adding 2½ years to one’s life expectancy – equating to 1 extra hour each day – or taking 2½ years off one’s “effective age”. Few studies compare these (increasingly popular) metaphors. Study 1 compared perception and comprehension between speed-of-ageing metaphors and hazard ratios. Study 2 compared the hazard ratio with three versions of effective age (change-in-age, personal, age-matched age). Results revealed a disadvantage to the change-in-age format (behaviour X makes someone Y years older), with unhealthy behaviours perceived as less risky, healthy behaviours as less beneficial, information judged less likely to affect behaviour and harder to understand. The personal format (behaviour makes your effective age X) shows no such disadvantage and is objectively better understood than hazard ratios. These results support the use of personalised effective ages in health and risk communication.