Fish Mercury Calculator

On average, about 14.7 micrograms (µg) of mercury per 4-ounce (~113 g) serving. The FDA/EPA technical table reports a mean of 0.13 ppm for canned light tuna, and canned light tuna is classified as a “Best choice” (2–3 servings per week). Actual cans vary — this is a population average, not a per-can measurement.

The highest averages in the FDA/EPA data are tilefish from the Gulf of Mexico (1.45 ppm), swordfish (1.00 ppm), shark (0.98 ppm), king mackerel (0.73 ppm), bigeye tuna (0.69 ppm), orange roughy (0.57 ppm), and marlin (0.49 ppm). All seven are on the FDA/EPA “Avoid” list for people who are pregnant, breastfeeding, or feeding young children — and are best avoided by everyone else too.

The U.S. EPA reference dose (RfD) for methylmercury is 0.1 µg per kilogram of body weight per day. For a 70 kg (154 lb) adult that works out to 49 µg per week. This calculator compares your estimated weekly intake from the fish you eat against that reference level — it is a screening estimate, not a medical diagnosis.

At a body weight of 70 kg, the EPA reference level allows roughly 3.3 4-ounce servings of canned light tuna per week — the tool rounds this down to whole servings. For comparison, one serving of canned albacore (white) tuna allows only about 1.2 servings per week at the same weight, because albacore averages 0.35 ppm versus 0.13 ppm for light tuna.

The FDA/EPA advice classifies canned albacore tuna as a “Good choice”: women who are pregnant or breastfeeding should limit it to 1 serving (4 oz) per week. One 4-ounce serving averages about 39.7 µg of mercury. This calculator is not medical advice — talk to your doctor about fish consumption during pregnancy.

The FDA/EPA advise serving fish to children ages 1–11 (it is an important source of nutrients), with age-appropriate portion sizes and the same category guidance: Best choices 2–3 servings a week, Good choices 1 serving a week, and Avoid-list fish none at all. Use this calculator with your child’s body weight — and for young children, check with your pediatrician.

No. Methylmercury binds to the protein in fish muscle, so it is not reduced by cooking, cleaning, skinning, or trimming the fat. (Trimming fat and skin helps reduce some other contaminants in locally caught fish, but not methylmercury.) The only way to reduce exposure is to eat less of high-mercury fish, or switch to lower-mercury species.

Canned light tuna (mostly skipjack) averages 0.13 ppm and is a Best choice. Canned albacore/white tuna averages 0.35 ppm and is a Good choice (limit 1 serving/week). Bigeye tuna averages 0.69 ppm and is on the Avoid list. A 4-ounce serving of bigeye tuna averages 78.2 µg of mercury — nearly 5.3 times the mercury of a light-tuna serving.

“Ppm” means parts per million: 1 ppm of mercury = 1 milligram of mercury per kilogram of fish, which is also 1 microgram per gram. So a 4-ounce (113.4 g) serving of fish at 0.13 ppm contains about 14.7 µg of mercury — multiply the table’s ppm by your serving weight in grams to get micrograms per serving.

No — they are averages across many tested samples, and individual fish vary widely. For example, FDA survey samples of swordfish ranged from not detected (ND) up to 3.22 ppm around the 1.00 ppm mean. The calculator intentionally uses the conservative FDA/EPA mean values and flags this uncertainty on every result.

This calculator only covers commercial fish in the FDA database. For locally caught fish, check your state or local fish consumption advisories first — contamination varies by waterbody. If no advisory information is available, the FDA recommends eating just one fish meal a week from local waters and no other fish that week.

The lowest averages in the FDA/EPA data include shrimp, scallop, oyster, sardine, tilapia, canned salmon, and squid (all around 0.01 ppm), followed by fresh/frozen salmon, catfish (0.02 ppm), and pollock (0.03 ppm). All are “Best choices” — safe for 2–3 servings per week under the FDA/EPA advice.

Because it is a screening tool built from population-average data. It cannot account for your personal health, other mercury sources (dental, occupational, local fish), or variation between individual catches. Decisions about fish consumption during pregnancy, breastfeeding, or for young children should be made with a qualified health professional.

Fish mercury averages and the Best/Good/Avoid categories come from the FDA/EPA technical table behind the official U.S. fish consumption advice (based on the FDA “Mercury Levels in Commercial Fish and Shellfish, 1990–2012” survey data). The exposure limit is the U.S. EPA reference dose for methylmercury: 0.1 µg per kg of body weight per day (IRIS). Links to both sources are in the methodology section below.