Fish Mercury Calculator (weekly mercury intake vs EPA reference dose)

Understanding the fish mercury calculator — concept and principle

This calculator estimates how much mercury you take in each week from the fish or seafood you eat and compares it with the US EPA reference dose for methylmercury. It is useful for people who are pregnant or planning pregnancy, breastfeeding mothers, parents of young children and anyone who eats a lot of fish.

Canned light tuna, 2 × 100 g: with the default inputs the result is 60% (25.2 ÷ 42 of the dose).

How it is calculated

Mercury per serving (µg) = mercury level (ppm) × serving size (g)

Mercury per week (µg) = per serving × servings per week

Reference dose for you (µg/week) = 0.1 µg/kg/day × 7 × body weight = 0.7 × body weight (kg)

Share of reference dose (%) = weekly mercury ÷ weekly reference dose × 100

ppm means micrograms per gram, so it multiplies directly with grams.
Mercury levels are the FDA's mean total-mercury values by species from US monitoring in 1990–2012.

The principle

Methylmercury builds up in fish through the food chain, so large, long-lived predators such as swordfish, shark and bigeye tuna carry the most, while small fish and shellfish carry little. In people it can harm the developing nervous system. The EPA reference dose is an intake believed to be without appreciable risk over a lifetime, and it already includes a ten-fold safety margin. Averaging over a week reflects that methylmercury leaves the body slowly.

Worked example

Default inputs: 60 kg, canned light tuna (0.126 ppm), 100 g servings, 2 servings a week.

Per serving = 0.126 × 100 = 12.6 µg.
Per week = 12.6 × 2 = 25.2 µg.
Reference dose = 0.7 × 60 = 42 µg/week.
Share = 25.2 ÷ 42 × 100 = 60%; average per day = 25.2 ÷ 7 ÷ 60 = 0.06 µg/kg/day.
Servings within the dose = floor(42 ÷ 12.6) = 3.

Each point is the calculator re-run with only “Your body weight (kg)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Your body weight (kg)	Share of EPA reference dose
15	240%
30	120%
45	80%
60	60%
75	48%
90	40%
120	30%

How to read the result

Where does your result fall?

Under 100% means your estimated intake is within the reference dose. A week slightly above it is not a reason for alarm, but regularly exceeding it is a reason to choose lower-mercury fish. Fish also provides protein, omega-3 fats and other nutrients, so the usual advice is to choose low-mercury species rather than avoid fish.

Common mistakes

Using raw weight for some meals and cooked weight for others inconsistently.
Assuming every fish of a species has the average level; large individuals can be much higher.
Forgetting fish eaten in sushi, sandwiches or mixed dishes.

Keep in mind: This is an estimate for general information, not medical advice. Follow your national food-safety advice, especially during pregnancy and for young children.

Frequently asked questions

Which fish are lowest in mercury?

Salmon, sardines, anchovies, shrimp, clams, oysters and pollock are among the lowest in the FDA data.

Is canned light tuna safer than albacore?

On average yes; light tuna is about 0.126 ppm and albacore about 0.35 ppm in the FDA data.

Does cooking remove mercury?

No. Methylmercury is bound in the muscle and is not removed by cooking.

Sources: US FDA, "Mercury Levels in Commercial Fish and Shellfish (1990–2012)" · US EPA IRIS, Methylmercury reference dose (0.1 µg/kg/day)

Checked 9 Nov 2026. US FDA, “Mercury Levels in Commercial Fish and Shellfish (1990–2012)” (fda.gov, mean mercury concentration in ppm by species); EPA IRIS reference dose for methylmercury of 0.1 µg/kg/day as used in FDA and EPA, “Response to External Peer Review on the FDA-EPA Technical Information on the Development of Fish Consumption Advice”.

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