A new NHS calculator will tell individuals how much longer they could live by making lifestyle changes.
The controversial tool predicts when you will have a heart attack or stroke - and compares a person's "heart age" with their biological age.
And it allows users to see what difference quitting smoking, losing weight, lowering blood pressure or cholesterol could make.
It comes as research on 575,000 people using the tool found that four in five had a "heart age" older than their actual age. Nearly nine in 10 men under 40 had a heart older than they were, compared to 4 in 10 women of the same age.
The original version of the calculator, launched last year, caused controversy because it handed out stark forecasts without showing how lifestyle changes could alter an individual's chances.
Health experts said the new version - hosted on www.nhs.uk - allowed users to see how they could boost their heart health by giving up smoking, or losing weight.
Dr Mike Knapton, associate medical director at the British Heart Foundation, said: "Knowing your heart age is vital to taking control of your health. Armed with this knowledge you can start to make changes to help protect yourself against cruel and life-changing events such as heart attack and stroke.
"The younger you start making small but significant changes, the greater the return on your in investment in your health."
Heart disease is the UK's single biggest killer, causing more than one quarter of all deaths each year. Factors like high blood pressure and high cholesterol, as well as smoking, diet and a lack of exercise, can increase the risk.
Keying information into the tool means a woman of 40 could be told that as a smoker, she had a heart age of 56, and is likely to have a heart attack or stroke by the age of 72. Quitting smoking would reduce that heart age to 51, and mean the forecast would add an extra six years.
Jamie Waterall, national lead for cardiovascular disease prevention, Public Health England, said: "Even though you may not have symptoms, having a heart age higher than your own age indicates an increased risk of serious illness. The Heart Age Tool gives an immediate indication of a person's potential risk and what they can start doing to reduce it."
Health officials encouraged those aged 40 and over to take up NHS healthchecks offered by GPs, which examine blood pressure and cholesterol levels.
Almost a million people have used the tool since its launch in 2015.
From today, the new version of the tool will recommend interventions and advice on how to lower cardiovascular risk. It can show how to reverse the ageing of the heart by, for example, stopping smoking.
It follows Spanish research showing that such forecasts are effective way to change behaviour, encouraging people to take more exercise, give up smoking or improve their diet.