I remember when I was trying to lose weight, I used to count calories in every food I ate. Although I do not recommend calorie counting, as I think it is not effective, I understand why most people do it.
If you are counting calories or simply trying to eat healthier, few ingredients are as universally loved as the tomato.
Whether layered on a sandwich, tossed into a salad, or grilled as a side dish, tomato slices add flavor, color, and nutrients without derailing your diet.
But when a recipe calls for “one slice,” or you’re logging your lunch into a food app, the question remains: Exactly how many calories are in a tomato slice?
The answer depends on the thickness of the slice and the size of the tomato. Here is the complete breakdown.
How Many Calories Are in a Tomato Slice?
Generally speaking, a single slice of tomato is incredibly low in calories. According to nutrition data from the University of Rochester Medical Center, a thick slice (about ½-inch thick) from a large tomato contains just 4.86 calories.
For a more standard, medium-thick slice weighing approximately 20 grams, you are looking at about 4 to 5 calories.
To put it simply:
- One slice of tomato = 4–5 calories.
Calories by Slice Size and Type
Because tomatoes come in different sizes, the calorie count can vary slightly depending on whether you are slicing a Roma or a Beefsteak.
Standard Slice (1/4-inch to 1/2-inch thick)
Thick Slice (1/2-inch thick from a large tomato)
Roma Tomato (Sliced)
- If you slice a medium Roma tomato into 4-5 slices, each slice contains roughly 5-6 calories. (Whole Roma: ~25 calories).
Beefsteak Tomato (Sliced)
- A large beefsteak tomato contains about 33 calories whole. If cut into 4-6 thick slices, each slice contains roughly 5-8 calories.
Full Nutrition Facts (Per Slice)
Beyond just calories, tomato slices offer a surprising amount of micronutrients. Here is the nutritional profile for one thick slice (0.5″ thick) as cited by the University of Rochester Medical Center:
| Nutrient | Amount | Daily Value (approx.) |
|---|---|---|
| Calories | 4.86 | N/A |
| Carbohydrates | 1.06 g | <1% |
| Protein | 0.24 g | <1% |
| Total Fat | 0.05 g | 0% |
| Fiber | 0.32 g | 1% |
| Sugar | 0.71 g | N/A |
| Potassium | 64 mg | 1% |
| Vitamin C | 3.4 mg | 4% |
| Vitamin A (IU) | 225 IU | 5% |
| Lycopene | 695 mcg | N/A |
Health Benefits of Eating Tomato Slices
Tomatoes aren’t just “empty calories.” They are considered a functional food packed with hydration and disease-fighting antioxidants.
Hydration
Tomatoes are composed of about 95% water. Eating them is a great way to stay hydrated, especially in the summer.
Rich in Lycopene
This antioxidant is what makes tomatoes red. It has been linked to reducing the risk of heart disease and supporting cardiovascular function.
Interestingly, cooking tomatoes (like grilling slices) can actually increase the bioavailability of lycopene.
Immune Support
A single slice contributes to your daily vitamin C intake, which supports your immune system and skin health.
How to Measure Calories Accurately
If you are tracking macros or calories strictly, measuring by “one slice” can be tricky because of varying thickness.
Use a Kitchen Scale
This is the most accurate method. Weigh your slices. According to the USDA and various nutrition databases, 1 ounce (28 g) of tomato contains roughly 5 calories. If your slices weigh 2 ounces, you are at 10 calories.
Standard Serving
A typical serving size recommendation for tomatoes is about 1 medium tomato or 5–6 slices, which totals approximately 20–25 calories.
Do Cooked or Grilled Tomato Slices Have More Calories?
If you grill your tomato slices without oil, the caloric difference is negligible.
- Raw Tomato Slices (100g): 18 calories.
- Grilled Tomato Slices (100g): 20 calories.
The slight increase is due to water loss during cooking, concentrating the remaining nutrients. However, calories can increase significantly if you add oil. One tablespoon of olive oil adds about 119 calories to your grilled tomatoes.
FAQ: How Many Calories Are in a Tomato Slice?
How many calories are in one slice of tomato for a burger?
A standard burger slice (1/4-inch thick, 20 g) contains approximately 5 calories.
Can I eat tomato slices on a keto diet?
Yes, in moderation. A tomato slice contains roughly 1 gram of carbohydrates. Tomatoes are generally considered keto-friendly as long as you stay within your daily carb limit, containing only 3-4 grams of net carbs per 100 g serving.
How many slices do you get from one tomato?
On average, you can get 4 to 6 slices from a standard medium-sized tomato, depending on how thick you cut them.
Are tomato slices healthy for weight loss?
Absolutely. They are considered a “low-calorie density” food. This means you can eat a large volume of them for very few calories, which helps you feel full while maintaining a calorie deficit.
How do tomato slices compare to cucumbers?
Both are low-calorie and hydrating, but tomatoes offer more vitamin C, potassium, and the antioxidant lycopene, which cucumbers lack.
What is the best way to store sliced tomatoes?
Unlike whole tomatoes (which should be kept at room temperature), sliced tomatoes should be stored in an airtight container in the refrigerator and consumed within 2-3 days to retain freshness and prevent spoilage.
Key takeaways: How Many Calories Are in a Tomato Slice?
Tomato slices are a nutritional powerhouse hiding behind a very low-calorie count. Whether you are adding them to a sandwich, a salad, or enjoying them grilled, you can rest easy knowing that each slice averages only 5 calories.
They provide essential vitamins, hydration, and antioxidants, making them one of the best ingredients you can add to your meals without worrying about your waistline.
