Do you realize how much you’re putting on your plate? You may think you have a handle on your portions, but it turns out people tend to underestimate how much they eat by as much as 25 percent. If you’re aiming for 2000 calories per day, that means you might be off by 500 calories, which could be the difference between losing or gaining a pound a week!

Most healthy eaters realize keeping an eye on portion sizes is an easy way, at a glance, to stay on track with weight goals. Still, it can be tricky. Part of the confusion is between serving size and portion size. They sound like the same thing, but generally there’s a big difference.

A serving size is a measured amount of food—1 cup, 1 slice, 1 teaspoon, etc. It’s the amount you’ll see on a food label, and it’s what the USDA uses in the Healthy Eating Guidelines and daily recommendations. Food label serving sizes are determined by the manufacturer, so they might not match the dietary guidelines. It’s a good idea to stick to what the guidelines say. 

A portion size is the amount of food or drink you consume in one sitting. It could be a large amount or a small amount; exactly one serving size, like a slice of bread, or several times that, like a bottle of fruit smoothie that says it contains two servings. (Who doesn’t guzzle the entire bottle in one go?)

Portion sizes have grown significantly over the years, placing value-for-money ahead of nutrition, and distorting the perception of how much one should actually be eating. Pop into your local movie theater and order a small soda and popcorn (delivering a total of 600 calories!), and it’s all too clear. But from breakfast to dinner, healthy foods to treats, portion distortion can be overcome. Here are six common measuring mistakes, with some fun and easy references to keep them in check.

If you’re using your cereal bowl as a guide, chances are you’re pouring too much. Even if you choose a healthy, high-fiber cereal, the calories and carbohydrates can quickly add up. Pick a sugary version, and you’ll start the day with an overload. Stick to about 1 cup (1 oz/30 g) of flaky cereal or ¼ cup (1 oz/30 g) of granola.

Granola: 1 serving = ¼ cup (1 oz/30 g), about the size of an egg | 140 calories
What to avoid: 1 full bowl (5 oz/155 g) | 700 calories
A 2000 calorie diet includes 6 servings of grains per day.
These can be spread throughout the day, so 2 servings at breakfast would be fine.

Nuts are full of goodness (healthy fats, protein, fiber), but they also deliver a large dose of fat and calories. Snack away, just stick to a small, closed handful once a day. The same goes for nut butters, which are an excellent afternoon pick-me-up—spread two tablespoons across your toast, not four.

Mixed nuts: 1 serving = small handful (1 oz/30 g), about the size of a golf ball | 160 calories
What to avoid: large overflowing handful (3 oz/90 g) | 480 calories
A 2000 calorie diet can include 1 serving of nuts five days a week.

Cheese is a perfect example of a healthy food that’s easy to overdo. Rich in calcium and protein, but high in saturated fat and sodium, it requires some restraint. Shredding or crumbling a small amount of a strong-flavored cheese, like sharp cheddar or feta, makes a little go a long way.

Colby cheese: 1 serving = 1½ oz (45 g), about the size of two 9V batteries | 165 calories
What to avoid: 4 thick slices (3 oz/90 g) | 330 calories
A 2000 calorie diet includes 3 servings of fat-free or low-fat dairy per day.

When it comes to grains, it’s easy to cover your entire dish and make them the star of the meal. Try to fill only one quarter of the plate with grains, and cast pasta or rice in a supporting role, as a side dish or scattered throughout a salad.

Cooked pasta: 1 serving = ½ cup (1 oz/30 g), about the size of a tennis ball | 120 calories
What to avoid: 4 cups (8 oz/250 g) | 960 calories
A 2000 calorie diet includes 6 servings of grains per day.
These can be spread throughout the day, so 2 servings at dinner would be fine.

Don’t be shy when digging into that salad! Most eaters don’t hit the daily recommendation for vegetables, so this is one instance where your portion can increase. Load up half your plate with greens, reds, and oranges.

Mixed greens: 1 serving = 2 cups (2 oz/60 g) leafy greens, about the size of 2 baseballs | 15 calories What to avoid: ½ cup (½ oz/15 g) | 4 calories
A 2000 calorie diet includes 2½ servings of vegetables per day

There’s no doubt it’s a better bet to eat your fruit rather than drink it, to get the most fiber and least sugar. But if you do slurp the freshly-squeezed kind every now and then, consider how many pieces of fruit you’re juicing in order to fill that glass—stick to one or two pieces.

Orange juice: 1 serving = 1 cup (8 fl oz/250 ml), about the size of a baseball | 110 calories
What to avoid: 1 large glass (16 fl oz/500 ml) | 220 calories
A 2000 calorie diet includes 2 servings of fruit per day.

What fun would life be without a little indulgence? But don’t be tempted to eat straight out of the tub, rather dish up a small scoop or two into a bowl. Throw on some fresh fruit or grated dark chocolate and use a small spoon to slowly, and mindfully, savor each delicious mouthful.

Vanilla ice cream: 1 serving = 2 small scoops (2½ oz/75 g), about the size of 2 golf balls | 155 calories
What to avoid: 4 large scoops | 390 calories
A 2000 calorie diet allows up to 270 calories per day from treat foods.

Challenge yourself: Get set up with balls, batteries, and measuring cups and see how your daily portion sizes stack up.