It's one of the most confusing things you face when trying to shed excess pounds.
For those looking to eat healthily, deciphering portion sizes can sometimes be a minefield as visualising just how much of certain foods you should be eating can be difficult.
But as confusing as they may be, keeping them in check is one of the key ways to prevent obesity.
Experts have said that a lack of portion control is one of the main reasons people are overweight – with many of us eating far more than we should be.
However there is now a simple way to keep an eye on how much food you're consuming, with FEMAIL's food portions graphic.
Research shows that one ounce of cooked rice is the same size as a tennis ball whilst the same amount of cooked pasta should be able to fill a cupcake wrapper.
The comparison data, which was published by McKinley Health Center, University of Illinois, US, has a list recommending portion sizes for various foods, which includes sizeequivalents for bread, pasta, snack foods, and fruits.
The next time you reach for the grapes, bear in mind that 15 grapes is the size of a lightbulb.
A portion of raisins is equivalent to one large egg whilst one ounce of cheese is the same size as a 9-volt battery.
When it comes to cooked meats, three ounces of beef, fish or poultry should be the same size as a deck of cards.
And three ounces of grilled or baked fish is the similar to the size of a chequebook.
When snacking, use your hands to measure just how much you can have.
Half a cup of crisps, crackers or popcorn is the size of a man's handful. To opt for less of the same, one-third is the same size as a woman's handful.
In their book, The Gastric Mind Band, Martin and Marion Shirran provide eye-opening examples of how portion control can make a huge difference to the waistline.
在马丁和马里昂·谢兰写的《胃脑同步》（The Gastric Mind Band）一书中，在书中列出了有启发性的例子，控制进食量对减肥有很大的效果。
They said: 'Spread butter on your toast, but be aware that a teaspoon of butter (enough for a thin layer) is 37 calories, but a tablespoon (a generous covering) is three times as much (111 calories).
'Put dressing on your salad, but learn to weight the vinegar in favour of the oil. A teaspoon of oil may be 45 calories, but a tablespoon is 135.
'That one extra tablespoon of oil every day amounts to a stone weight gain over a year.'
'Switch to sweetener in your tea or coffee. Cutting out two spoons of sugar in your tea three times a day creates an annual calorie deficit of 37,000 calories, which could be enough to shed more than 11lb.
'Have ice cream occasionally, but just one scoop (about 150 calories) and never eat it straight from the tub.
'Enjoy a few nuts with a drink, but stop at one or two (a small 4oz bag will set you back 600 calories).