A good everyday rule is:

½ plate vegetables/fruits + ¼ plate protein + ¼ plate whole grain or starch + small amount of healthy fat.
This matches the basic MyPlate/Healthy Eating Plate approach.

Simple serving size guide

FoodGood serving sizeVisual cueVegetables1 cup cooked/raw or 2 cups leafy greens1–2 fistsFruit1 medium fruit or 1 cup cut fruit1 fistProtein3–4 oz fish, chicken, turkey, lean meatPalm of your handBeans/lentils½ cup cooked½ fistEggs1–2 eggs—Whole grains½ cup cooked rice, oats, quinoa, or pastaCupped handBread1 sliceFlat palmPotato/sweet potato½–1 mediumComputer mouseNuts1 ozSmall handfulNut butter1–2 tablespoonsThumb-sizedOlive oil1 tablespoonThumb tipCheese1–1.5 oz2 diceYogurt/milk1 cup1 fist/cup

The American Heart Association uses similar serving examples: vegetables are generally 1 cup raw/cooked or 2 cups leafy greens, fruit is often 1 cup or 1 medium fruit, and protein ounce-equivalents include 1 egg, 1 oz cooked meat/fish/poultry, ¼ cup beans, or ½ oz nuts/seeds.

Daily target for many adults

For a basic 2,000-calorie pattern:

Food groupDaily goalVegetables2½ cupsFruit2 cupsGrains5–6 oz equivalents, mostly whole grainProtein foods5–6 oz equivalentsDairy/calcium-rich foodsAbout 3 cupsOils/healthy fatsSmall amounts, around 5–6 teaspoons

These targets vary based on age, sex, body size, activity level, and goals.

Easiest rule

At each meal, aim for:

Protein + plants + fiber-rich carb + healthy fat

Example:
Grilled chicken or salmon + broccoli/salad + sweet potato or brown rice + olive oil or avocado.