A medium fresh tomato (about 123 grams) contains fewer than 5 grams of total carbohydrates, making it a smart choice for low-carb and keto diets.
Most people assume a tomato is somewhere between a lettuce leaf and an apple on the carb scale. That vagueness leads to confusion at the grocery store and on the dinner plate.
The actual number is surprisingly low. A medium fresh tomato contains fewer than 5 grams of total carbohydrates. Since tomatoes vary wildly in size from grape to beefsteak, the real answer depends on which one you picked up.
Carb Count Varies By Tomato Size
A single 0.3-gram grape tomato is a completely different portion from a 7-gram large slicing tomato. Despite the size range, the carb density per 100 grams stays remarkably consistent.
One hundred grams of raw tomato (roughly one medium fruit) provides about 3.8 to 3.9 grams of total carbohydrates. The fiber content sits around 1.2 grams of that total, meaning the net carb load is even smaller.
The remaining carbs are mostly natural sugars like glucose and fructose. This naturally low sugar content is precisely why tomatoes are considered a low-carb fruit option in most dietary plans.
Why the Serving Size Matters for Accuracy
Most people do not eat just one standard serving of tomatoes, especially when building a salad or preparing salsa. Tracking the pieces you actually eat is the most accurate method for counting.
- Grape or cherry tomatoes: One grape tomato has 0.3g of carbs, while one cherry tomato has 0.7g. A handful of ten cherry tomatoes provides roughly 7g of total carbs.
- Plum or Roma tomatoes: These egg-shaped tomatoes contain about 2.4g of carbs each. They are a medium-density option often used for cooking or canning.
- Medium slicing tomato: A standard 123-gram medium fruit carries about 4.8g to 5g of total carbs and 1.2g of protein.
- Large tomato: A three-inch diameter large tomato can contain approximately 7g of total carbohydrates, about the same as a small apple.
- Chopped tomato: One cup of chopped tomato (roughly 180g) totals about 7g of carbs and provides a significant lycopene and vitamin C boost.
Portion control is the only variable that matters here. Weighing the raw ingredient once gives you a repeatable data point for every future recipe.
Net Carbs and the Glycemic Impact
Understanding Net Carbs
Total carb count is one metric, but net carbs are often more relevant for blood sugar management. Net carbs subtract the indigestible fiber from the total carbohydrate figure.
A medium tomato provides about 3 to 4 grams of net carbs. This small insulin response makes it a non-issue for most metabolic diets. Medical News Today has a helpful breakdown of the carbs in grape tomato varieties if you regularly eat the smaller kinds.
The Glycemic Index Factor
The glycemic index of a fresh tomato is roughly 23 to 30, which classifies it as a very low glycemic food. Foods with a GI under 55 are digested slowly and have a minimal impact on blood sugar levels.
| Tomato Type | Total Carbs | Net Carbs (approx.) |
|---|---|---|
| Grape (1 fruit) | 0.3 g | 0.3 g |
| Cherry (1 fruit) | 0.7 g | 0.6 g |
| Plum / Roma (1 fruit) | 2.4 g | 1.9 g |
| Medium (123 g) | 4.8 g | 3.6 g |
| Large (3-inch) | 7.0 g | 5.5 g |
| 1 cup chopped | 7.0 g | 4.6 g |
These small carb loads make it simple to include tomatoes in a low-carb meal plan without worrying about blood sugar spikes or exceeding daily limits.
Fitting Tomatoes Into a Low-Carb or Keto Plan
Most low-carb and keto plans allow between 20 and 50 grams of net carbs per day. Fresh tomatoes fit easily into that budget, but mindful tracking keeps portions in check.
- Count the pieces: Logging two large plum tomatoes (4.8g total) uses a tiny fraction of your daily carb budget and provides fresh flavor.
- Watch for added sugars: Fresh tomatoes are safe, but canned sauces, sun-dried tomatoes, and ketchup often have added sugars that spike the carb count quickly.
- Balance the meal: Pair tomatoes with healthy fats like olive oil and a source of protein to further blunt the glucose response at mealtime.
- Check your tolerance: Some very strict keto dieters prefer to stick to 100-gram servings to stay well under their net carb limit without guessing.
If you are diabetic or prediabetic, the trace carbs in tomatoes are generally not a concern. Some research suggests consuming about 200g of raw tomatoes daily may have beneficial effects on managing blood sugar levels.
Raw Versus Cooked: Does the Count Shift?
Cooking tomatoes does not change their fundamental carbohydrate content. The sugars remain stable through heat processing, so the numbers stay largely the same.
The biggest change comes from water loss. When you roast or sun-dry tomatoes, the water evaporates but the carbs remain, making the dried product much denser by weight. A sun-dried tomato has far more carbs per gram than its fresh counterpart.
For raw consumption, the nutritional density is perfect. Healthline’s full profile of the carbs in a medium tomato confirms the total is roughly 4.8 grams for a typical 123-gram fruit.
| Serving Size | Total Carbs | Fiber |
|---|---|---|
| 100 g raw | 3.8 g | 1.2 g |
| 1 cup chopped | 7.0 g | 2.4 g |
| 1 large (3-inch) | 7.0 g | 1.5 g |
The Bottom Line
A fresh tomato is a low-carb, nutrient-dense food that fits comfortably into most dietary patterns. The exact carb count depends entirely on the size of the fruit, but even a large tomato contains only about 7 grams of total carbohydrates.
If you are managing diabetes or strictly counting net carbs for a ketogenic diet, a registered dietitian or certified diabetes educator can help you determine your personal tolerance to tomato sugars based on your own blood sugar responses.
References & Sources
- Medical News Today. “Carbs in Tomatoes” One grape tomato contains 0.307 grams of carbohydrates.
- Healthline. “Carbs in a Medium Tomato” Carbs comprise 4% of raw tomatoes, which amounts to fewer than 5 grams of carbs for a medium specimen (123 grams).