The World Health Organisation (WHO) recommends doing 150-300 minutes (2.5-5 hours) of moderate intensity exercise per week OR 70-150 minutes (1-2.5 hours) of vigorous physical exercise per week. This should be a combination of both cardiovascular exercise (increase in heart rate and breathing rate) and strength training.
During moderate intensity exercise your heart rate is raised and you can still maintain a conversation. During vigorous physical activity you shouldn’t be able to hold a conversation.
To keep it simple, aiming for 30 minutes of exercise per day will give you the benefits of lower rates of mortality, cardiovascular disease, type 2 diabetes, cancer and depression.
If you’re pregnant, post-partum, have poor cardiac health or haven’t exercised in 6 months care should be taken when getting back into exercise. When starting back with exercise it is advised to gradually increase the duration and intensity of sessions with the guidance from a healthcare practitioner or fitness professional.
If you’d like any more information check out the WHO recommendations here: https://www.who.int/dietphysicalactivity/factsheet_adults/en/