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Fish Mercury Calculator

Choose smaller, shorter-lived fish rather than less fish — sardines carry a fortieth of swordfish.

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Share of the reference dose142.9%above it — this is a sustained average, not a single meal
Weekly portion at the reference dose140 gAlbacore tuna, canned white at 0.35 ppm, for a 70 kg adult
Mercury in your portion70 µg
Weekly allowance49 µg
The same weight of salmon instead8.98%of the reference dose — a fortieth of swordfish
And of sardines5.31%
The right response to mercury is usually to choose smaller, shorter-lived species rather than to eat less fish — the omega-3 benefits are large and well established. Pregnancy is where the advice tightens sharply, and that is worth taking from a clinician.

The formula

intake = grams * ppm / days ; reference dose = 0.1 ug per kg of body weight per day

Mercury concentrates up the food chain

Methylmercury is not excreted quickly, so each level of the food web carries what it ate. A swordfish that has spent years eating smaller fish that ate smaller fish still carries a hundred times the concentration of a sardine. Size and lifespan predict mercury far better than species does.

The reference dose has a wide safety margin

The EPA sets it at 0.1 µg per kilogram of body weight per day, and that already includes a tenfold factor below the level where effects were observed. Exceeding it occasionally is not a poisoning; it is using up margin that exists to be used. The advice is about a sustained average rather than any single meal.

The fish are still worth eating

This is the part that gets lost. The omega-3 benefits of fish consumption are well established and large, and for most people most of the time the right response to mercury is to choose smaller species rather than to eat less fish. Salmon, sardines and shrimp carry a fortieth of swordfish's mercury and more of the omega-3. Pregnancy is the case where the advice tightens sharply, and it is worth taking from a clinician rather than a calculator.

How much to trust a footprint

Life-cycle figures for the same product routinely differ by a factor of two between studies, because deciding what to count — the farm, the packaging, the shop, the drive home, the disposal — is a methodological choice rather than a measurement. The numbers here are central estimates from published meta-analyses. They are reliable for comparing one option against another, which is what people actually use them for, and not reliable to the second significant figure.

The other thing worth keeping in view is scale. Individual choices matter and they are not where the emissions are: the difference between the best and worst quartile of beef producers is larger than most people's entire dietary footprint, and that is a question about agriculture policy rather than about shopping.