Carbs in tomatoes come out to about 5 grams total per medium fruit. Once fiber is subtracted, that drops to roughly 3 grams of net carbs.
That is low enough that most low carb plans barely notice a tomato. The details behind that number matter more once a diet gets strict about counting.
Carbs in tomatoes, by size
USDA data for a medium raw tomato, about 123 grams, lists 5 grams of total carbohydrate. It also lists 2 grams of dietary fiber and 3 grams of total sugar.
Those figures come from the USDA’s seasonal produce guide. It is one of the few federal sources that lists a tomato’s carbs per whole fruit rather than per 100 grams.
A small tomato, closer to 90 grams, runs a bit lower. A large tomato, past 180 grams, pushes carbs up toward 7 or 8 grams total.
Cherry and grape tomatoes carry the same ratio per gram. They are simply spread across more small fruit per handful.
A cup of halved cherry tomatoes lands close to the same 5 to 6 grams a single medium slicer does. Weight drives the number.
Variety does not change it much. A yellow, striped, or deep red tomato of the same size carries close to the same total carbohydrate regardless of color.
What net carbs actually means here
Net carbs is total carbohydrate minus fiber. Fiber passes through digestion largely unabsorbed, so it does not raise blood sugar the way starch or sugar does.
For a medium tomato, that is 5 grams total minus roughly 2 grams of fiber. The result lands around 3 grams net.
No single federal agency prints an official net carb figure on a nutrition label. This number is a calculation.
It is built from USDA’s own total carbohydrate and fiber data. It is not a label claim on its own, just simple subtraction applied to numbers that already exist.
Diabetic carb counting works the same way in practice. Fiber gets pulled out of the total before anyone estimates the effect on blood sugar.
The CDC’s guidance on healthy eating with diabetes treats that distinction as central to the whole approach. A tomato’s fiber is doing real work in that math.
Are tomatoes low carb enough for keto
Most low carb frameworks treat anything under 5 grams of net carbs per serving as an easy fit. Keto plans use that same rough cutoff.
A medium tomato at roughly 3 net grams clears that bar. The catch is portion creep.
A big beefsteak tomato sliced onto a burger adds up. A handful of cherry tomatoes in a salad the same day adds more.
Both together can stack into 10 or more net grams before dinner is over. That is still modest against a typical keto daily target of 20 to 50 total grams.
It just is not free. Sauce, paste, and sun dried tomatoes concentrate the same sugars into a smaller volume.
Their carb count per tablespoon runs much higher than fresh fruit. A tablespoon of tomato paste alone can carry 3 grams of carbohydrate.
That is close to what a whole medium tomato has. A recipe built around paste, not fresh fruit, needs its own separate count.
Where a tomato’s carbs actually come from
Almost none of a tomato’s carbohydrate is starch. The bulk splits between natural sugars and structural fiber.
Those sugars are mostly glucose and fructose, in close to equal amounts. The fiber sits in the skin, the cell walls, and the gel around the seeds.
Sugar content rises as a tomato ripens on the vine. A green tomato pulled early carries less sugar than the same fruit left to fully color up.
It also carries slightly more starch. Neither shift moves the total carb count by much in either direction.
Cooking down a tomato into sauce does not add carbohydrate on its own. It just removes water.
That process concentrates every gram already there into a smaller serving size. Nothing new is created in the pot.
How tomato carbs compare to other vegetables
A tomato’s total carb count sits below a raw carrot or beet by a wide margin. It sits well below any starchy vegetable like potato or corn.
It also sits close to cucumber and bell pepper, two other watery, low starch fruits eaten as vegetables. That places tomatoes in the group most low carb diets treat as close to unrestricted.
Leafy greens still carry fewer grams per cup. Tomatoes are not far behind them.
Onions and garlic, both common tomato dish partners, carry noticeably more carbohydrate per cup than a tomato does. A sauce built from tomato, onion, and garlic gets most of its carb count from the onion, not the tomato it is named after.
That is worth remembering before blaming a jar of sauce entirely on the tomatoes inside it. The aromatics usually carry a bigger share of the total than most people assume.
For a fuller nutrient rundown, the full nutrient breakdown for a raw tomato covers protein, vitamin content, and calories per serving. It is worth reading alongside this page, not instead of it.
Carbs in tomatoes across a real day of eating
A person watching net carbs closely does not need to skip tomatoes. Two or three medium tomatoes spread across a day add up to around 9 grams net.
That is a small slice of most daily carb budgets. The bigger swing usually comes from what sits next to the tomato, not the tomato itself.
Bread, rice, and sweetened dressings move the needle far more than the fruit carrying them. A sandwich fails a low carb count because of the bread, rarely the slice of tomato inside it.
For anyone building a stricter keto plan around tomatoes, the longer keto specific breakdown walks through serving sizes and common substitutions. It covers more ground than fits here.
Someone tracking blood sugar rather than a fixed keto target has a different set of priorities. How tomatoes fit a blood sugar focused diet covers that angle directly, including where fiber content helps slow absorption.
Checking the number instead of guessing it
Recipes rarely specify grams. A kitchen scale does not always come out for a single tomato.
Converting a recipe’s cup or ounce measurement into an actual gram count removes most of the guesswork. That step matters more for tomatoes than most produce.
Size varies so widely fruit to fruit that a cup measurement alone can hide a real gram swing. Weighing once and remembering the number solves that for good.
Potassium content follows a similar per gram pattern to carbs, scaling up with size rather than variety. How much potassium the same tomato carries is worth a look for anyone tracking more than one nutrient at once.
A quick cup to gram conversion tool turns a recipe measurement into the number this page is built around. A real gram count beats an eyeballed guess every time a total actually matters.
Why the fiber matters as much as the sugar
Two foods can share the same total carbohydrate and still behave very differently in the body. Fiber content is the reason.
A tomato’s roughly 2 grams of fiber per medium fruit is unusually high relative to its total carb count. That ratio is part of why carbs in tomatoes rarely trigger a sharp blood sugar response.
None of this makes a tomato a fiber supplement on its own. One medium tomato covers a small fraction of a typical daily fiber target.
It does mean the sugar inside arrives more slowly. Sugar from a source with little or no fiber around it hits differently.
That pacing is part of the appeal for anyone managing blood sugar day to day. It is a small effect, but a real one.
Canned and dried tomatoes carry a different count
A cup of canned diced tomatoes runs close to what an equal weight of fresh fruit does. Canning mostly adds liquid, not sugar.
The carb count per cup stays fairly similar to fresh. Canned crushed and canned whole peeled tomatoes follow the same pattern.
Read the label anyway, since some brands add a small amount of sugar or citric acid during processing. That addition is usually small but not always zero.
Diced, crushed, and whole peeled tomatoes differ mostly in texture, not carb content. They start from the same fruit and skip any real sweetener.
A recipe swapping between the three forms rarely needs to adjust a carb count because of the switch. Texture, not carbohydrate, is what changes between them.
Sun dried tomatoes are a different story entirely. Removing almost all the water concentrates the same sugar into a fraction of the original volume.
A small handful of dried pieces can represent several whole fresh tomatoes worth of pulp. Portion size matters far more for dried forms than for fresh fruit.
Tomato juice sits somewhere in between fresh fruit and paste. A cup of juice packs the pulp of more than one tomato, so its carb count per cup runs higher than a single fresh tomato’s does.
Frequently asked questions
How many carbs are in one whole tomato?
A medium tomato, about 123 grams, carries roughly 5 grams of total carbohydrate and 2 grams of fiber. That works out to about 3 grams of net carbs.
Do cherry tomatoes have fewer carbs than a regular tomato?
Gram for gram, no. A cup of halved cherry tomatoes lands close to the same total carb count as one medium slicing tomato.
Are tomatoes considered low carb on a keto diet?
Yes. A tomato runs roughly 3 grams of net carbs per medium fruit, well under the 5 gram cutoff most keto guidelines use per serving.
Does cooking a tomato change its carb count?
Cooking does not add carbohydrate, but it removes water. That concentrates the existing sugar and fiber into a smaller volume.
What has more carbs, tomato sauce or a fresh tomato?
Sauce and paste carry more carbs per tablespoon than fresh tomato. Cooking concentrates the same sugars into far less volume, while a whole fresh tomato spreads that carbohydrate across a larger, more filling serving.