A raw tomato is not actually a potassium powerhouse. A cup of tomato juice, on the other hand, edges out a banana.
That gap surprises most people. It comes down entirely to concentration, not some hidden nutrient that only shows up in the processed version.
This guide covers the real potassium numbers for tomatoes. It covers every common form, from the raw fruit to paste, and what those numbers mean for blood pressure and daily intake.
The short version
A medium raw tomato contains about 292 milligrams of potassium. That is roughly 6 percent of the daily value, a respectable but unremarkable middle tier among vegetables.
Processed tomato products tell a different story. A cup of canned stewed tomatoes carries about 528 milligrams. A cup of tomato juice carries about 527 milligrams.
Both numbers come from federal dietary data. Both also beat a medium banana’s 451 milligrams per cup equivalent.
Potassium itself matters for blood pressure regulation. Most American diets fall well short of the daily target.
The raw tomato number
The National Institutes of Health Office of Dietary Supplements lists a medium raw tomato at 292 milligrams of potassium. That works out to about 6 percent of the daily value.
A separate USDA dietary data table puts raw tomato at 287 milligrams per 100 grams. That translates to 158 milligrams for a half medium fruit.
The two figures line up closely. That is reassuring, since food composition data can vary between sources.
For context, that same USDA table ranks baked potato at 531 milligrams per 100 grams. Spinach comes in even higher, at 636 milligrams.
Raw tomato sits comfortably below both. It lands closer to carrots and broccoli than the true high potassium tier.
Why processed tomato products change the math
Concentration is the entire story here. Stewing, juicing, and pasting all remove water while keeping the mineral content.
A cup of the processed product represents more actual tomato than a cup of raw slices ever could. Federal dietary guidance data puts a cup of canned stewed tomatoes at 528 milligrams of potassium.
A cup of 100 percent tomato juice comes in nearly identical, at 527 milligrams. Both of those numbers edge out a medium banana, listed by the same source at 451 milligrams.
That comparison surprises people. Banana has such a strong reputation as the potassium food that it feels wrong for a can of stewed tomatoes to beat it, even by a small margin.
Tomato paste concentrates the fruit even further than juice or stewed tomatoes do. A small spoonful goes a long way nutritionally, even in the smaller servings people actually cook with.
What potassium actually does
The NIH fact sheet on potassium ties the mineral directly to blood pressure management. Higher intake supports vasodilation, and it helps the body excrete more sodium through urine.
Both effects work against high blood pressure. The DASH eating pattern is built around roughly three times the potassium of a typical American diet.
In clinical research, that pattern lowers systolic blood pressure by an average of 5.5 points. Diastolic pressure drops by about 3 points on average, a meaningful effect rather than a marginal one.
Adult daily targets sit at 3,400 milligrams for men and 2,600 milligrams for women. Most American diets fall well under those numbers.
That gap is part of why potassium rich foods, tomato products included, get singled out in dietary guidance.
The kidney disease exception
Potassium is not automatically good for everyone in unlimited amounts. People with impaired kidney function process potassium differently.
Excess levels can build up in the blood instead of being excreted normally. The NIH fact sheet is direct about this.
Its general intake recommendations do not apply to people with conditions like kidney disease. Anyone at risk of high blood potassium should consult a physician or registered dietitian instead.
For the specific numbers that matter to a kidney conscious diet, see this site’s guide to tomatoes and renal diets at https://knowtomato.com/tomatoes-renal-diet/.
Frequently asked questions
How much potassium is in a raw tomato?
About 292 milligrams in a medium tomato, roughly 6 percent of the daily value, according to the National Institutes of Health. A separate USDA data table gives a closely matching figure of 287 milligrams per 100 grams.
Does tomato juice really have more potassium than a banana?
Yes, slightly. Federal dietary data lists a cup of tomato juice at 527 milligrams of potassium, compared to 451 milligrams in a medium banana.
Why is potassium higher in tomato juice or stewed tomatoes than in a raw tomato?
Concentration. Juicing and stewing remove water while keeping the mineral content, so a cup of the processed product represents more actual tomato than a cup of raw slices.
How much potassium do adults need per day?
The adequate intake is 3,400 milligrams for adult men and 2,600 milligrams for adult women, according to NIH dietary guidance. Most American diets fall short of that target.
Is high potassium from tomatoes a concern for anyone?
Yes, specifically people with impaired kidney function. NIH guidance states that its general potassium recommendations do not apply to people with kidney disease, who should get personalized guidance from a physician or dietitian.
Bottom line: potassium in tomatoes is real, but the raw fruit is the modest version of the story. A cup of tomato juice or canned stewed tomatoes delivers noticeably more, enough to edge past a banana on the same measure, thanks to concentration rather than any special processing magic. For most healthy adults working toward the daily potassium target, that makes tomato products a genuinely useful, easy addition, with one honest exception. Anyone managing kidney disease should treat that same concentration as a reason for caution instead.
SOURCES
National Institutes of Health, Office of Dietary Supplements: Potassium, Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/
U.S. Department of Agriculture, Food Surveys Research Group, via NCBI Bookshelf: Potassium Content of Selected Foods per 100 Grams and for Common Measures. https://www.ncbi.nlm.nih.gov/books/NBK587683/table/usdaddb47.tab2/
Dietary Guidelines for Americans, a joint publication of the Department of Health and Human Services and the Department of Agriculture: Food Sources of Potassium, Standard Portions. https://www.dietaryguidelines.gov/sites/default/files/2024-08/Food-Sources-Potassium-Standard-508C.pdf