Net Carbs in Tomatoes: Per Tomato, Per Cup, and By Type
Tomatoes are low in net carbs. A medium raw tomato has around 3.3g of net carbs — making it one of the most practical vegetables for low-carb and keto diets. This page focuses specifically on net carbs: what they are, how they are calculated for tomatoes, and what the numbers look like across every common serving size and product. The full macro and micronutrient profile is on the Tomato Nutrition Facts page.
Quick Answer: Net Carbs in a Tomato
A medium raw tomato (about 123g) contains approximately 3.3g of net carbs. Per 100g, raw tomatoes have around 2.7g of net carbs. That number comes from subtracting 1.2g of dietary fiber from 3.9g of total carbohydrates.
- Per 100g (raw): ~2.7g net carbs
- Medium tomato (123g): ~3.3g net carbs
- One cup chopped (180g): ~4.8g net carbs
- Cherry tomato (17g): ~0.5g net carbs
- Large beefsteak tomato (182g): ~4.9g net carbs
What Net Carbs Actually Means
Net carbs are the carbohydrates your body actually digests. Dietary fiber is a carbohydrate that passes through the digestive system largely unabsorbed, so it does not raise blood glucose the way digestible carbs do. Subtracting fiber gives you a more accurate number for managing blood sugar or staying in ketosis.
The formula is straightforward: Net Carbs = Total Carbohydrates − Dietary Fiber. Tomatoes have a low total carb count to begin with, and fiber makes up a meaningful portion of that — which is why the net carb figure ends up noticeably lower than the total. Note that tomatoes contain no sugar alcohols, so there is nothing else to subtract beyond fiber.
Net Carbs by Serving Size
These values are for raw, whole tomatoes with no added ingredients. Data is sourced from the USDA FoodData Central database.
| Serving | Weight | Total Carbs | Dietary Fiber | Net Carbs |
|---|---|---|---|---|
| 1 cherry tomato | 17g | 0.7g | 0.2g | 0.5g |
| 1 plum / Roma tomato | 62g | 2.4g | 0.7g | 1.7g |
| 1 medium round tomato | 123g | 4.8g | 1.5g | 3.3g |
| 1 large beefsteak tomato | 182g | 7.1g | 2.2g | 4.9g |
| 1 cup chopped raw tomato | 180g | 7.0g | 2.2g | 4.8g |
| 1 cup cherry tomatoes | 149g | 5.8g | 1.8g | 4.0g |
| 100g raw tomato | 100g | 3.9g | 1.2g | 2.7g |
Net Carbs by Tomato Variety
Most fresh tomato varieties fall within a narrow net carb range of 2.7g to 3.5g per 100g. Denser, sweeter varieties like grape tomatoes sit at the higher end. Large, water-heavy varieties like beefsteak sit at the lower end per 100g — though their bigger overall size means more net carbs per whole fruit.
| Tomato Type | Total Carbs per 100g | Fiber per 100g | Net Carbs per 100g |
|---|---|---|---|
| Standard round / slicing | ~3.9g | ~1.2g | ~2.7g |
| Cherry tomato | ~4.0g | ~1.1g | ~2.9g |
| Grape tomato | ~4.5g | ~1.0g | ~3.5g |
| Roma / plum tomato | ~3.8g | ~1.1g | ~2.7g |
| Beefsteak tomato | ~3.9g | ~1.2g | ~2.7g |
| Heirloom tomato | ~3.9–4.8g | ~1.0–1.3g | ~2.8–3.6g |
| Green (unripe) tomato | ~5.1g | ~1.1g | ~4.0g |
Green tomatoes are higher in net carbs than ripe ones because unripe fruit contains more starch. That starch converts to sugar as the tomato ripens, but the total carb count drops slightly in the process since some carbon is lost through respiration. The carbs in tomatoes page covers the full sugar and starch composition by variety.
How Processing Changes Net Carbs
Cooking and processing do not add net carbs to tomatoes — they concentrate them. When water is removed through heat, reducing, or drying, the carbs and fiber that remain get packed into a smaller volume. The net carb count per gram rises, even though nothing was added.
The fiber-to-carb ratio also shifts in some products. Juicing, for example, strips away most of the fiber while keeping most of the sugars — which pushes net carbs up relative to total carbs in a way that plain cooking does not.
Net Carbs per Serving in Common Tomato Products
| Tomato Product | Net Carbs per 100g | Typical Serving | Net Carbs per Serving |
|---|---|---|---|
| Raw tomato | 2.7g | 1 medium (123g) | ~3.3g |
| Canned whole tomatoes (no salt) | 2.5g | ½ cup (120g) | ~3.0g |
| Crushed tomatoes (canned) | 3.9g | ½ cup (122g) | ~4.8g |
| Tomato sauce (plain, canned) | 5.7g | ¼ cup (61g) | ~3.5g |
| Tomato paste | 14.5g | 1 tbsp (16g) | ~2.3g |
| Tomato juice (unsalted) | 3.8g | 1 cup (244g) | ~9.3g |
| Sun-dried tomatoes (dry pack) | 43.5g | ¼ cup (27g) | ~11.7g |
| Stewed tomatoes (no added sugar) | 5.8g | ½ cup (127g) | ~7.4g |
Tomato paste looks high at 14.5g net carbs per 100g, but a tablespoon serving (16g) brings that down to just 2.3g. The per-100g number is misleading without the serving context. Tomato juice is the more surprising one — a full cup reaches 9.3g of net carbs because juicing removes almost all the fiber that would normally soften the number. The canned tomatoes nutrition page has a complete breakdown of every major canned and jarred tomato product.
Net Carbs, Blood Sugar, and Glycemic Load
Tracking net carbs matters most for people managing blood glucose. Tomatoes have a glycemic index of around 15, which is very low. According to the American Diabetes Association, low-GI foods cause a slower, more gradual rise in blood sugar compared to high-GI foods. A medium tomato has a glycemic load of around 1 — effectively negligible.
The low GI is partly explained by the fiber content. Fiber slows digestion, which reduces how quickly sugar enters the bloodstream. This is why net carbs alone do not tell the whole story — fiber quality matters too. The fiber in tomatoes page goes deeper on fiber type and digestive impact.
Net Carbs in Tomatoes for Keto Diets
Most ketogenic approaches cap daily net carbs at 20g to 50g. A medium tomato at 3.3g net carbs uses roughly 7% to 17% of that daily budget. That leaves plenty of room to include tomatoes in meals without breaking ketosis in most people.
Cherry tomatoes are worth watching on strict keto — not because they are high in net carbs, but because they are easy to eat in large quantities. A cup of cherry tomatoes is 4g of net carbs, which adds up if you are grazing throughout the day. A handful of 5–6 cherry tomatoes sits under 2.5g net carbs, which is a very manageable snack portion.
Practical Net Carb Reference for Keto
- 2 cherry tomatoes: ~1.0g net carbs
- ½ medium tomato sliced on a salad: ~1.6g net carbs
- 1 medium tomato in a meal: ~3.3g net carbs
- 1 cup chopped tomato in a sauce base: ~4.8g net carbs
- 2 tbsp tomato paste: ~4.6g net carbs
- ½ cup tomato sauce (plain, canned): ~3.5g net carbs
Frequently Asked Questions
What are the net carbs in a tomato?
A medium raw tomato (about 123g) has approximately 3.3g of net carbs. That is 4.8g of total carbohydrates minus 1.5g of dietary fiber.
How do you calculate net carbs in tomatoes?
Subtract dietary fiber from total carbohydrates. For a medium tomato: 4.8g total carbs minus 1.5g fiber equals 3.3g net carbs. The same formula applies to every tomato product listed in the table above.
Are tomatoes low in net carbs?
Yes. A full cup of chopped raw tomatoes contains under 5g of net carbs. Tomatoes are among the lower net-carb vegetables available, largely because they are about 95% water and contain meaningful fiber relative to their small carb count.
How many net carbs are in cherry tomatoes?
One cup of cherry tomatoes (about 149g) contains approximately 4.0g of net carbs. A single cherry tomato has roughly 0.5g of net carbs.
How many net carbs are in tomato paste?
Tomato paste has approximately 14.5g of net carbs per 100g. A standard tablespoon serving (16g) brings that down to about 2.3g — a small and manageable amount in most recipes.
How many net carbs are in tomato juice?
Tomato juice has about 3.8g of net carbs per 100g, but a one-cup serving (244g) adds up to around 9.3g. Juicing removes most of the fiber, which raises the effective net carb count compared to eating a whole tomato.
Can you eat tomatoes on a keto diet?
Yes, in normal portions. A medium tomato contributes about 3.3g of net carbs toward a typical daily keto limit of 20–50g. Concentrated tomato products like paste, sauce, and juice need portion tracking due to their higher net carb density.
Do cooked tomatoes have more net carbs than raw?
Per gram, yes. Cooking removes water, which concentrates both the carbs and fiber into a smaller mass. The net carb count per cup is higher for cooked tomatoes because a cooked cup is denser than a raw cup — not because new carbs appeared.
Related Tomato Nutrition Guides
- Tomato Nutrition Facts – Complete Guide
- Calories in Tomatoes
- Carbs in Tomatoes
- Fiber in Tomatoes
- Sugar in Tomatoes
- Canned Tomatoes Nutrition
- Lycopene in Tomatoes
- Potassium in Tomatoes
Bottom Line
A medium raw tomato has about 3.3g of net carbs — the result of subtracting 1.5g of fiber from 4.8g of total carbohydrates. Net carb counts stay low and consistent across all fresh tomato varieties. They rise significantly only in concentrated products like tomato paste and sun-dried tomatoes, and even then, normal serving sizes keep the per-meal impact manageable. For the complete tomato nutrition breakdown across all nutrients, visit the Tomato Nutrition Facts page.