What this calculator does
The Fish Mercury Intake Calculator estimates how many micrograms (µg) of mercury you take in from a single serving of fish or seafood. Mercury, mostly in the form of methylmercury, accumulates in fish tissue and is a concern for pregnant people, nursing parents and young children. This is a general, country-neutral nutrition tool; the safe-limit comparison uses the widely cited EFSA/JECFA provisional tolerable weekly intake.
How to use it
Enter your fish serving size in grams (a typical serving is about 140–170 g), then enter the mercury concentration in micrograms per gram (µg/g). Concentration values come from food-safety databases: low-mercury fish such as salmon are around 0.02 µg/g, while higher-mercury fish such as fresh tuna or swordfish can reach 0.3–1.0 µg/g. Optionally enter your body weight to see your weekly tolerable limit and what fraction of it this serving uses.
The formula explained
The core calculation is simply $$\text{Mercury (µg)} = \text{Serving (g)} \times \text{Concentration (µg/g)}$$ The weekly limit uses the provisional tolerable weekly intake of 1.6 µg of methylmercury per kilogram of body weight, so a 70 kg adult has a limit of 112 µg per week. Dividing the serving's mercury by that limit gives the percentage shown.
Worked example
Suppose you eat a 200 g portion of fish with a mercury concentration of 0.5 µg/g. Mercury \(= 200 \times 0.5 = \mathbf{100}\) µg. For a 70 kg adult the weekly limit is \(70 \times 1.6 = 112\) µg, so this one serving uses \(100 / 112 \approx 89\%\) of the weekly tolerable intake.
FAQ
Is methylmercury the same as the mercury in a thermometer? No. The health concern in fish is organic methylmercury, which is absorbed efficiently and accumulates in the body.
Which fish are lowest in mercury? Salmon, sardines, anchovies, shrimp and tilapia are generally low; shark, swordfish, king mackerel and large tuna are high.
Is this medical advice? No. It is an educational estimate; follow guidance from your local food-safety authority and your doctor, especially during pregnancy.
