Body Weight of Koi per Unit Increasing Length
Concept: Most medications are dosed on a milligrams per kilogram level.
Koi weight varies tremendously with body conformation (slender pond-grade fish vs. massive Japanese show koi), but the following table gives a reasonable average weight estimate for a healthy, well-grown koi.
IMPORTANT: You can WEIGH a koi by filling a vat or container of water on a scale and getting the weight of that container of water – =OR= “taring” the container of water to ZERO. Then put the koi you’re weighing into that container and use the difference in weight as the weight of the fish. But the following chart is pretty useful. It’s been checked AND checked again as an average.
What contributes to the “average”? Lots of things:
- Gender
- Pregnancy
- Feeding intensity and quantity
- Environmental size or other factors affecting growth.
- Bloodline
- Conformation (Imposing, slender, deep bodied, etc.)
| Length (inches) | Avg. Weight (kg) |
|---|---|
| 4 | 0.01 |
| 6 | 0.04 |
| 8 | 0.11 |
| 10 | 0.23 |
| 12 | 0.4 |
| 14 | 0.65 |
| 16 | 1.1 |
| 18 | 1.8 |
| 20 | 2.5 |
| 22 | 3.75 |
| 24 | 4.75 |
| 26 | 6.75 |
| 28 | 7.5 |
| 30 | 9.5 |
| 32 | 10.5 |
| 34 | 12.5 |
| 36 | 15.0 |
| 38 | 19.0 |
| 40 | 24.0 |
A useful rule of thumb is that koi weight increases roughly with the cube of length, so a 30-inch koi isn’t merely 50% heavier than a 20-inch koi—it’s typically more than three times heavier. That’s why medication dosing by estimated weight can become wildly inaccurate if length alone is used.
