Watermelon is a refreshing, hydrating fruit that's surprisingly low in calories for its volume. But if you're tracking your intake, you need to know exactly how many calories are in your serving — whether it's a cup of diced cubes, a wedge, or a whole melon. This calculator takes the guesswork out of portioning by letting you enter your serving size in cups, grams, or ounces, and it instantly returns the calories, along with a breakdown of carbs, sugar, and other key nutrients.
Perfect for meal preppers, fitness enthusiasts, and anyone following a calorie-controlled diet, this tool uses USDA nutrition data for raw watermelon. You can also adjust for the edible portion — since you won't eat the rind — and even compare a single serving to your daily calorie needs. Just pick your unit, enter the amount, and hit Calculate to see your personalized nutrition snapshot.
🍉 Watermelon Serving Calculator
If you don't eat the rind, keep at 100%. For wedges with rind, lower to ~60%.
How to Use This Calculator
Start by entering the amount of watermelon you plan to eat. You can choose between cups of diced fruit, grams, or ounces. If you're using a kitchen scale, grams are the most accurate. For a typical wedge, you can estimate the edible portion — the flesh only — by setting the edible percentage to about 60% if you're including the rind in your weight. The calculator then converts everything to grams and applies USDA nutrition values per 100 grams.
Optionally, enter your daily calorie goal to see what percentage of your daily intake this serving represents. This is handy for meal planning or weight management. After clicking Calculate, you'll see the total calories, a breakdown of macronutrients, and the serving size in grams.
Nutrition Facts for Watermelon
According to the USDA FoodData Central, raw watermelon contains approximately 30 calories per 100 grams. It's about 91% water, which is why it's so refreshing and low in energy density. The carbohydrate content is roughly 7.55 grams per 100 grams, with about 6.2 grams of naturally occurring sugar. Fiber is modest at 0.4 grams, and protein is about 0.61 grams. Fat is negligible at 0.15 grams.
Watermelon is also a good source of vitamin C and provides some vitamin A, potassium, and lycopene — an antioxidant linked to heart health. Because it's mostly water, it can help with hydration, but it's not a significant source of protein or fiber.
Worked Examples
Example 1: You eat 1 cup of diced watermelon (152 grams). With 100% edible portion, the calculator gives 45.6 kcal, 11.5 g carbs, 9.4 g sugar, 0.6 g fiber, 0.9 g protein, and 0.2 g fat.
Example 2: You have a 10-ounce wedge that includes the rind. If you set edible portion to 60%, the edible weight is 170 grams. Calories come to 51 kcal, with 12.8 g carbs and 10.5 g sugar.
Example 3: For a 2000-calorie diet, a 2-cup serving (304 g) provides 91 kcal, which is about 4.6% of your daily goal.
Tips for Accurate Portioning
- Use a digital kitchen scale for the most precise measurements, especially if you're tracking macros.
- When using cups, lightly pack the diced cubes — don't press them down.
- If you buy pre-cut watermelon, check the package weight and divide by the number of servings.
- Remember that the rind is not typically eaten, so adjust the edible percentage accordingly.
Common Questions
Is watermelon high in sugar?
Watermelon has about 6 grams of sugar per 100 grams, which is moderate compared to other fruits. However, because it's mostly water, a typical serving doesn't spike blood sugar as much as dried fruits or juices. The glycemic load is relatively low.
Can I eat watermelon on a low-carb diet?
It depends on your carb limit. A 1-cup serving has about 11.5 grams of net carbs (carbs minus fiber). If you're on a strict keto diet (under 20 g carbs), you'd need to limit your portion. For moderate low-carb plans, it can fit.
Does the variety affect calories?
Different varieties (seedless, yellow, etc.) have very similar calorie counts. The USDA values are a good average.
Why Use This Calculator?
This tool saves you time and helps you stay consistent with your nutrition goals. Instead of looking up tables or guessing, you get an instant, personalized estimate. It's especially useful for athletes, dieters, and anyone who wants to enjoy watermelon without derailing their calorie budget.
For more fruit nutrition tools, check out our watermelon calorie calculator or explore other serving-based calculators like the grapefruit calories per ounce calculator.