Watermelon Calories & Nutrition Calculator

Raw watermelon has 30 kcal per 100g — one of the lowest calorie densities of any food. Only lemon (29 kcal), celery (14 kcal), and cucumber (15 kcal) are meaningfully lower, and those are far less commonly eaten in large volumes. Watermelon's 91.5% water content means you are essentially eating flavored water with dissolved sugar and micronutrients ^[1].

One cup of diced watermelon (152g) provides 46 kcal. A standard wedge (1/16 of a melon, 286g) has 86 kcal — less than a medium apple (95 kcal) despite being over 50% heavier. Ten watermelon balls (122g) have just 37 kcal. At summer gatherings, a generous plate of watermelon (300-400g) still registers under 120 kcal.

For food journaling, watermelon is straightforward to track but easy to underestimate by volume. The key number is 30 kcal per 100g — roughly half the calorie density of most common fruits (apple 52, banana 89, mango 60). If you can estimate or weigh your portion in grams, multiply by 0.30 for calories.

Watermelon contains 4,532mcg (4.5mg) lycopene per 100g — approximately 76% more than raw tomato (2,573mcg). Lycopene is the red-pigmented carotenoid responsible for watermelon's color, and it varies by cultivar: seedless varieties tend to contain more lycopene than seeded types. USDA data shows this value is for red-fleshed varieties; yellow watermelon contains negligible lycopene ^[1][2][3].

Unlike tomato, where lycopene bioavailability increases significantly with cooking (heat breaks cell walls and the oil medium aids absorption), watermelon is almost exclusively consumed raw. Despite this, the absolute lycopene content per typical serving is substantial: a cup of diced watermelon (152g) delivers 6,889mcg lycopene — more than a cup of raw cherry tomatoes (3,835mcg) ^[4].

For food journaling, standard nutrition panels do not display lycopene. If tracking carotenoid intake, note that watermelon is one of the most concentrated food sources available at any calorie level — you get 4.5mg lycopene per 30 kcal, whereas tomato provides 2.6mg per 18 kcal.

Watermelon has 6.2g total sugar per 100g, which accounts for 82% of its total carbohydrates (7.55g). The sugar profile is fructose-dominant: 3.4g fructose (55%), 1.6g glucose (26%), and 1.2g sucrose (19%). This fructose dominance contributes to watermelon's perceived sweetness — fructose is roughly 1.7x sweeter than glucose by weight ^[1][5].

One cup of diced watermelon (152g) has 9.4g total sugar — less than a medium apple (18.9g), a banana (14.4g), or a cup of grapes (23.4g). The high sweetness-to-calorie ratio makes watermelon taste more indulgent than its calorie count suggests. A full wedge (286g) has 17.7g sugar — still modest compared to most fruit servings.

For food journaling, watermelon's sugar content is proportional to portion weight. At 6.2g per 100g, even a generous 500g serving (common at cookouts) has just 31g sugar and 150 kcal — roughly equivalent to a 350ml soft drink in sugar but with substantially more water volume and micronutrients.

Watermelon has 0.4g dietary fiber per 100g — the lowest among common fruits. Apple has 2.4g, orange has 2.4g, and banana has 2.6g. Even grapes (0.9g) have more than double. The near-absence of fiber means watermelon contributes minimal bulk to the digestive tract compared to other fruits ^[1].

Protein is similarly minimal at 0.61g per 100g (2% of calories), though per calorie this is actually comparable to many fruits (apple is 0.26g at 52 kcal). Total fat is negligible at 0.15g. The practical result is that watermelon is almost entirely water and carbohydrates — 91.5% water, 7.6% carbs, 0.6% protein, 0.2% fat.

For food journaling, watermelon should be tracked primarily as a hydration-plus-sugar food rather than a significant source of fiber, protein, or fat. If fiber tracking matters, pair watermelon with fiber-rich foods — a cup of watermelon (152g, 0.6g fiber) plus a cup of strawberries (144g, 2.9g fiber) provides a better nutritional mix.

A whole watermelon (approximately 4,518g edible flesh from a 15" × 7.5" melon) contains 1,355 kcal, 341g total carbohydrate, 27.6g protein, and 5,060mg potassium per the USDA standard reference. This means a person eating one-eighth of a whole watermelon (~565g) consumes roughly 170 kcal and 35g sugar — comparable to a 350ml serving of a sweetened beverage in sugar content ^[1].

At social gatherings, watermelon consumption can be difficult to estimate. Useful benchmarks: a standard wedge (1/16 melon, ~286g) = 86 kcal; a thick slice (1/8 melon, ~572g) = 172 kcal; a generous plate serving (400-500g) = 120-150 kcal. Children's portions (100-200g) range from 30-60 kcal.

For food journaling at events, the simplest approach is to estimate the fraction of a whole melon consumed. One-sixteenth (a standard wedge) = 86 kcal is a reliable benchmark. If you eat two wedges, log 172 kcal. The calorie density is low enough that even rough estimates produce acceptable journaling accuracy.