5 g0.18 oz
Nemo weighs about 5 g (0.011 lb), but that is our estimate: Pixar has never given his size or weight. He is a young ocellaris clownfish, and we assume he is about 6 cm (2.4 in) long. Measured wild clownfish of that length weigh around 4.7 g, so 5 g is a fair round number.
| Fully grown, 11 cmMaximum length on FishBase, reached by the largest females | 30 g1.06 oz |
|---|---|
| Adult size, 8 cmMeasured length-weight formula | 11.4 g0.4 oz |
| Our estimate for Nemo, 6 cmFormula gives 4.7 g, rounded to 5 g | 5 g0.18 oz |
| 6 cm by FishBase’s general formulaEstimated from body shape, not from weighed fish | 3.1 g0.11 oz |
| Smaller Nemo, 4 cmMeasured length-weight formula | 1.4 g0.049 oz |
There is no official number. Pixar has never stated how long or heavy Nemo is, in Finding Nemo (2003) or since, so this is our calculation. What the film does establish: Nemo and his father Marlin are ocellaris clownfish (Amphiprion ocellaris), Nemo is a young fish on his first day of school, and in the dentist’s aquarium Gill picks him to jam the filter because he is the smallest of the tank gang.
Real ocellaris clownfish grow to at most 11 cm (4.3 in). Nemo is drawn clearly smaller than his father, so we put him at about 6 cm (2.4 in). That length is the guess in this estimate; everything after it is measured data.
A 2018 study weighed and measured 65 wild ocellaris clownfish from Pulau Tioman, Malaysia, and found that weight follows W = 0.0197 × L^3.06, with W in grams and L the total length in cm. For 6 cm: 6 to the power 3.06 is about 241, and 241 × 0.0197 is 4.7 g. We round that to 5 g, which is 0.011 lb or about 0.18 oz.
The study found the clownfish keeps the same body shape as it grows, so its weight rises with the cube of its length. Double the length and the weight goes up about eight times. A 4 cm Nemo would weigh only 1.4 g, an 8 cm adult about 11.4 g, and the very largest 11 cm fish around 30 g.
FishBase gives a second, general formula for the species, W = 0.01445 × L³, worked out from the body shape of similar fish rather than from weighed clownfish. It gives a lighter 3.1 g for a 6 cm fish (0.01445 × 216). We go with the measured formula, but either way Nemo weighs a few grams.
Ocellaris clownfish live in small groups in a sea anemone, ranked by size. The breeding female is the biggest, the breeding male comes second, and the smaller males stay small: the dominant fish suppress their growth. All clownfish start out as males, and when the female dies the breeding male turns into a female.
That means a real Marlin would have become female after Coral died. Adam Summers, the biologist who advised Pixar on both films, has said the team knew this but left it out because it would confuse young viewers.
About 0.011 lb, or 0.18 oz. That is our estimate of 5 g for a young clownfish 6 cm long, roughly the weight of a US nickel.
Pixar never said. We estimate about 6 cm (2.4 in), since he is a young fish drawn smaller than his father, and adult ocellaris clownfish reach at most 11 cm (4.3 in).
An ocellaris clownfish, Amphiprion ocellaris, also called the common or false percula clownfish. In the wild it lives among sea anemones on reefs, usually 3 to 15 m deep.
Ocellaris clownfish grow to about 11 cm (4.3 in), and only the dominant female in a group gets that big. By the measured length-weight formula, an 11 cm fish weighs around 30 g (1.1 oz).
Yes. Clownfish are all born male, and when the breeding female dies her male partner changes sex to take her place. Pixar’s fish adviser chose not to show this in the film.
Last checked October 2, 2026.
