Larry Lunsford

There are times when you need to know how much your Koi weigh. Such as when calculating doses of medications or when determining how much to feed. The most accurate way to determine your Koi's weight is to actually weigh it. Sometimes this is not practical, so you can use the chart below to estimate weight vs. length for a normal build Koi. Length is from tip of nose to tip of tail. Keep in mind that this table is for typical Koi. A skinny Koi of a given length may weigh 25% to 50% less than a typical Koi. A fat Koi of a given length could weigh 25% to 50% more than a typical Koi. You'll have to judge where your Koi falls on the skinny-normal-fat scale. If you loose the chart, use the 12-12 rule: a typical 12" long Koi weighs 12 ounces. To calculate the weight of other length Koi, use the formula: weight = length x length x length / 144 (weight is in ounces, length is in inches from tip of nose to tip of tail).

Along with knowing how much your Koi weigh now, you may want to predict how much they will weigh in the future. Having some idea of future weight will help you make decisions such as "When do I need to upgrade my filter?" and "How big does my filter need to be?" Growth rates vary greatly. The chart below shows some (very rough) Koi lengths (in inches) for three situations: maximum growth, normal pond, and low growth. In the maximum growth scenario, the Koi are kept in water that is around 70° F to 75° F year round and are fed around 5% of their body weight daily (spread out over 8 to 12 feedings). The normal pond rate assumes that the Koi are fed twice a day in warm weather, less in the spring and fall, and none in winter. The low growth scenario assumes that the Koi are fed a little every few days in summer.