If you always feel tired, maybe it’s time to turn to science for a proven way to get a better night of shut-eye.

Psychologist and sleep scientist Jason Ellis and a team at the Northumbria Centre for Sleep Research teamed up with Nectar Sleep to break down what makes a great night’s sleep great.

We all know how important enough sleep – and the quality of that sleep – is to our everyday lives. "From concentration to creativity levels, and even how we approach challenging situations, good quality sleep can have such a positive impact on a number of things," says Ellis.

But if you’re not getting good enough sleep and you don’t know why, the scientists may have found a way to determine the factors you may need to change or adjust.  "People might be surprised at how much better they can actually sleep," notes Ellis.

So, calculator at the ready – here’s what you need to know about the different elements that, together, determine how well you sleep…

Sleep duration
Optimum for ideal sleep: 7-9 hours

We are all different, so some of us will only need seven hours, while others feel knackered unless they have nine. The best way to judge this is simply to question how you feel in the morning.

Sleep efficiency
Optimum: More than 85%

Sleep efficiency is time spent in bed asleep, divided by time spent in bed overall. So if you spend eight hours in bed and four hours asleep in bed, you have a 50% sleep efficiency. This includes dozing or waking up in the middle of the night.

Social jet lag (aka lie-ins)
Optimum: Fewer than 60 minutes

To minimise disruption to sleep patterns, the researchers say to minimise lie-in time to less than an hour.

Sleep environment
Optimum: 22 degrees C, minimal light and noise below 40db

Aside from a temperate, dark and quiet room, the mattress should also be comfortable and supportive, to minimise the risk of tossing and turning.

Sleep routine behaviour
Optimum: No caffeine six hours prior, no activities two hours before bed

Basically, late night activities are a no-no. Ditch the tea and coffee habit after lunchtime, don’t smoke (if you do) 30 minutes before bed and make sure all your work activities, exercise, and eating is done and dusted two hours before you get tucked up in bed.

Sleep disturbance criteria
To take into account: Factors that contribute to a bad night sleep

These include whether a person has a recognised sleep problem, uses medicine or alcohol to aid sleep, feels drowsy in the day or has a partner with a sleep problem.

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Now for the maths

You could aim for the above and you’d stand a good chance of a refreshing slumber, or you could get really technical about it. The scientists say the optimal ‘score’ for the perfect night’s sleep is 18.

Your score is calculated by adding two points if you manage the optimal SD (sleep duration), two for the ideal SE (sleep efficiency), and three for less than one hour of SJL (social jet lag).

Next, you get a maximum of seven points for the ideal SEC (sleep environment); this is made up of two points for 22 degrees C, one for no noise, one for no light, one for no electronic use, and two points for a comfortable bed.

Lastly, there’s an additional four points for ideal SRB (sleep routine behaviour); which includes one point for not working within two hours of bed, one for no food or exercise within two hours of bed, one for no caffeine within six hours, and one for no smoking within 30 minutes of sleep.

If you’re still with us, you need to add that number up and divide it by the SDC (sleep disturbance criteria). If you consider yourself too plagued by any of the factors mentioned above then each ‘disturbance’, like a partner with a sleep problem, is worth one point. Divide your previous score by that number for your final result.

Or in a nutshell: (SD + SE + SJL + SEC + SRB) / SDC = a perfect night’s sleep.

If you can’t be bothered with any of that, take this online quiz instead.

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What the numbers mean

If you got 18, well done you – you’re officially a great sleeper, according to science. If you got less than that, your calculations can help you work out where you can make changes to improve your score, and therefore your sleep.