Inshore saltwater

Tarpon

Megalops atlanticus. Also called silver king.

Length to weight chart, typical size by age, and how to photograph a tarpon so fishline measures it well.

Typical top length: 72 in; about 117 lb
A 54 inch fish: 49.2 lb; 49 lb 3 oz
Age at 54 inches: about 14 years; rough, varies by water
Growth levels off: about age 40; gains slow to a crawl after

Tarpon length to weight chart

Estimated weight for a tarpon in average shape at each length, from the formula W = L^3 / 3,200 (W in pounds, L in inches). It is the same relationship fishline uses when it measures a tarpon from a photo.

Tarpon length to weight chart
Length	Weight	Lb and oz	Rough age
24 in	4.3 lb	4 lb 5 oz	about 4 years
28 in	6.9 lb	6 lb 14 oz	about 5 years
32 in	10.2 lb	10 lb 4 oz	about 6 years
36 in	14.6 lb	14 lb 9 oz	about 7 years
40 in	20.0 lb	20 lb	about 8 years
44 in	26.6 lb	26 lb 10 oz	9 to 10 years
48 in	34.6 lb	34 lb 9 oz	about 11 years
52 in	43.9 lb	43 lb 15 oz	12 to 13 years
56 in	54.9 lb	54 lb 14 oz	about 15 years
60 in	67.5 lb	67 lb 8 oz	about 18 years
64 in	81.9 lb	81 lb 15 oz	about 22 years
68 in	98.3 lb	98 lb 4 oz	about 29 years
72 in	117 lb	117 lb	40+ years
76 in	137 lb	137 lb	40+ years

Total length, nose to the tip of the pinched tail. Weights are for a tarpon in average shape. A fat fish, like a female before the spawn, weighs more and a thin one less, which a girth measurement picks up. Rows past 72 inches are bigger than typical for the species.

Size by age

fishline's growth model puts a typical tarpon at around 72 inches when fully grown, with most of its growth done by about age 40. Younger fish add length fast; older fish mostly add weight.

Age from length is rough. Fish in warm water with plenty to eat grow faster than this, and fish in cold or crowded water grow slower. For a quick estimate from any length, use the fish age calculator.

Typical tarpon size by age
Age	Length	Weight
1 year	6.9 in	0.10 lb
2 years	13.1 in	0.69 lb
3 years	18.7 in	2.0 lb
4 years	23.7 in	4.2 lb
5 years	28.3 in	7.1 lb
6 years	32.5 in	10.7 lb
8 years	39.6 in	19.5 lb
10 years	45.5 in	29.5 lb
12 years	50.3 in	39.8 lb
15 years	55.9 in	54.7 lb
20 years	62.3 in	75.4 lb
25 years	66.1 in	90.2 lb
30 years	68.4 in	100 lb
40 years	70.7 in	110 lb

From a von Bertalanffy growth curve. Fish in warm, food-rich water grow faster than this and fish in cold or crowded water grow slower, so treat every row as a rough middle.

Weigh your tarpon

Enter the length, and the girth if you taped it, for an estimate on your fish.

Enter a lengthPick the species and type the length in inches. The weight shows up here, with the formula behind it and a rough age.

Photo tips for tarpon

fishline reads length from the photo using whatever is in frame for scale, so a clean, side-on shot gives the tightest number.

1Lay the fish on the deck or a wet board next to a cooler or a measuring sticker, and shoot straight down from above.
2On a hand-held photo keep your arms in and the fish level with your chest. A fish held out toward the camera looks much bigger than it is, and fishline has to undo that.
3Get the tail in. Total length runs to the tip of the tail, so a cropped tail means a short read.
4Big tarpon are best photographed in the water alongside the boat. Some states require it, so check your local rules.

More in how to take a fish photo that measures well.

More inshore saltwater

Or skip the tape. Snap a photo and fishline measures it.

Species, length and weight from one photo. 5 free measurements every month.

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