Koi Feeding Calculator
Work out how much to feed your koi today. The right amount depends far more on water temperature than on the fish — enter your koi, their size and the pond temperature, and the calculator gives a daily weight, a feeding schedule and the food type to use.
🍽 Koi Feeding Calculator
Results update as you type. Water temperature drives everything here — measure the pond, not the air.
Seasonal temperatures
Set a typical pond temperature for each part of the year to see how sharply the feeding plan changes. Real pond temperatures depend on your climate, depth and shade, so measure rather than assume.
How to Use the Koi Feeding Calculator
Four inputs, and the temperature is the one that matters most.
Count and measure
Number of koi and their average length, nose to tail fork. Weight is estimated from length, so a rough average is fine.
Take the water temperature
From the pond, in the morning. Air temperature and forecasts are not a substitute — a deep pond lags the air by days.
Choose a goal
Growth feeding only if the filter can take it. Maintenance is the safer setting for adult fish or a pond under pressure.
Weigh the food once
Weigh the daily amount on a kitchen scale, see what it looks like in the scoop, then use the scoop from then on.
How Much Should I Feed My Koi?
Koi feeding is usually expressed as a percentage of body weight per day, and that percentage is set almost entirely by water temperature. Koi are cold-blooded: their metabolic rate, their digestive enzymes and the gut bacteria they rely on all work at the speed the water permits. At 75 °F a koi can process 2 percent of its body weight a day comfortably. At 50 °F the same fish struggles with a quarter of that, and food sitting undigested in a cold gut causes real harm.
So the daily amount comes out of three things:
- Total biomass — how many koi, and how big they are. A single 24 inch koi weighs as much as thirty 6 inch ones, which is why counting fish tells you almost nothing on its own.
- Water temperature — which sets the percentage of that biomass they can process per day.
- What the filter can absorb — every gram of food becomes ammonia within a day or two. Feeding for growth on a filter sized for maintenance simply moves the problem into the water.
Estimating weight from length is standard practice, since almost nobody weighs their koi. A reasonable approximation for a healthy koi is weight in grams ≈ 0.018 × (length in cm)³, which puts a 12 inch koi at around 510 g (1.1 lb) and a 24 inch koi at around 4 kg (9 lb). Body shape varies with variety, sex and condition, so treat the figure as a good estimate rather than a measurement.
Koi weight and daily ration by length
| Koi length | Approximate weight | Daily food at 2% |
|---|---|---|
| 6 in (15 cm) | 64 g (0.14 lb) | 1.3 g |
| 10 in (25 cm) | 295 g (0.65 lb) | 5.9 g |
| 14 in (36 cm) | 809 g (1.78 lb) | 16.2 g |
| 18 in (46 cm) | 1,720 g (3.79 lb) | 34.4 g |
| 20 in (51 cm) | 2,360 g (5.20 lb) | 47.2 g |
| 24 in (61 cm) | 4,078 g (8.99 lb) | 81.6 g |
Six 14 inch koi at 2 percent is about 97 grams of pellets a day — roughly a small handful, split across three feeds. Written down like that, most people find they have been feeding considerably more.
Koi Feeding Chart by Water Temperature
The single most useful table in koi keeping. Find your pond temperature, read across.
| Water temperature | Daily ration | Feedings per day | Food type | Notes |
|---|---|---|---|---|
| Below 41 °F (5 °C) | None | 0 | — | Digestion has effectively stopped. Do not feed. |
| 41–50 °F (5–10 °C) | 0.25% | Every 2–3 days | Wheat germ | Only if fish are visibly active and asking. Skip it otherwise. |
| 50–59 °F (10–15 °C) | 0.5% | 1 | Wheat germ | Spring and autumn. Easily digested, low protein. |
| 59–68 °F (15–20 °C) | 1.0% | 2 | Staple | Transition period. Watch that the filter keeps pace. |
| 68–77 °F (20–25 °C) | 2.0% | 3 | Growth / high protein | Peak season. Best growth and colour development. |
| 77–86 °F (25–30 °C) | 2.5% | 3–4 | Growth / high protein | Maximum intake, but oxygen is now the limiting factor. |
| Above 86 °F (30 °C) | 1.0% | 2 | Staple | Reduce feeding. Warm water holds little oxygen; add aeration and shade. |
Notice the shape of it. Feeding rises steeply from 59 °F to a peak in the mid-70s, then falls away again above 86 °F — not because the fish cannot digest the food, but because a hot pond cannot supply the oxygen that digesting it requires. The high end and the low end both call for restraint, for completely different reasons.
When to Stop Feeding Koi in Winter
Stop feeding when the pond is consistently below about 50 °F (10 °C), and stop entirely below 41 °F (5 °C). The reason is mechanical rather than dietary: below roughly 50 °F a koi's digestive system slows to the point where food can sit in the gut without being processed, and food that sits in a cold gut can cause serious internal problems. A koi that goes into winter with reserves and an empty gut is in a much better position than one that was fed a fortnight too long.
Some practical points for the transition:
- Go by water temperature, not the calendar. A mild November can keep a pond above 50 °F for weeks after people have stopped feeding, and a cold snap in October can take it below.
- Switch to wheat germ first. Wheat germ based foods are lower in protein and digest more easily at cool temperatures. Move to them in the 50–59 °F band rather than waiting.
- Use the morning reading. Pond temperature peaks in the afternoon. The morning figure is the honest one for deciding whether to feed that day.
- Watch the fish, not just the thermometer. Koi that do not come up for food are telling you they do not want it. Uneaten pellets in cold water just rot.
- Spring is the mirror image, but slower. Restart with wheat germ once the pond is reliably above 50 °F, feed sparingly, and expect the filter bacteria to take weeks to catch up. Spring is when most koi health problems appear, because the fish's immune response recovers more slowly than the parasites do.
The 5-Minute Rule
The traditional advice is to feed only what the koi finish in about five minutes, and it is good advice as a check. It is a poor plan on its own, though, because koi will keep eating well past what is good for them, especially in warm water and especially when several people feed the same pond.
Use both. Weigh the calculated daily amount once, note what it looks like in your scoop, and then use the five-minute rule to confirm the fish are actually eating it. If food is still floating after five minutes, feed less. If the calculated amount vanishes in thirty seconds, that is normal — it does not mean the koi are underfed.
Koi Food Types by Season
- Wheat germ (spring and autumn). Lower protein, easily digested at cool temperatures. The right food between roughly 50 and 59 °F, and the one to switch to first in autumn and last in spring.
- Staple (transition and hot weather). Balanced everyday food for the 59–68 °F range and for the height of summer when you are deliberately reducing intake.
- Growth / high protein (summer). Higher protein for the 68–86 °F peak season, when koi put on most of their annual growth. Only worth using with filtration that can handle the waste.
- Colour enhancing. Usually contains spirulina or similar carotenoid sources. Used in warm months alongside growth food; too much can affect white ground in some varieties.
- Treats. Lettuce, watermelon, orange segments and prawns are fine occasionally in warm water. They are not part of the daily ration and should not be fed when the pond is cool.
Buy pellet sizes the fish can actually take, keep food dry and cool, and replace it each season — fish food oxidises, and a bag left open in a shed over winter loses much of its vitamin content by spring.
Overfeeding, Oxygen and Water Quality
Nearly every koi pond problem that is not a stocking problem is a feeding problem. Every gram of food becomes ammonia within a day or two, either through the fish or through uneaten pellets breaking down. In summer that lands on a filter already working at its limit, in a pond that holds less oxygen than it did in spring.
The warning signs are recognisable: ammonia or nitrite that will not sit at zero, nitrate climbing between water changes, green water and string algae that resist every treatment, a filter that clogs faster than it used to, and fish at the surface at dawn. If you are seeing these, cutting feeding by half for a week is the fastest diagnostic available — and if the readings improve, you have your answer. Test with the water parameter checker before and after so you are working from numbers rather than impressions.
Frequently Asked Questions
The koi feeding questions that come up every spring and every autumn.
Related Koi Pond Tools
Feeding, stocking and water quality are the same problem seen from three angles.
Koi Pond Stocking Calculator
The biomass you are feeding is the biomass the pond has to support. Check it.
Water Parameter Checker
Test before and after a feeding change so you are working from numbers.
Koi Pond Calculator
Pond volume in gallons and litres, the figure everything else depends on.
Fish Feeding Calculator
Feeding portions and schedules for aquarium species rather than pond koi.
Check your stocking level if water quality slips in summer, use the water parameter checker after any change in feeding, and see the koi fish care guide for the full seasonal routine. Keeping small koi indoors first? The koi fish tank guide covers that stage.
Methodology and accuracy
Koi weight is estimated from length using weight in grams ≈ 0.018 × (length in cm)³, a cubic length-weight relationship with a condition factor typical of healthy koi. Real weight varies with variety, sex, age and condition, so treat the biomass figure as a close estimate rather than a measurement. If you can weigh a representative fish, use that instead.
Daily rations are drawn from temperature-banded feeding guidance widely used in koi keeping: no feeding below 41 °F, 0.25% every two to three days from 41–50 °F, 0.5% daily from 50–59 °F, 1.0% from 59–68 °F, 2.0% from 68–77 °F, 2.5% from 77–86 °F, and back to 1.0% above 86 °F where dissolved oxygen becomes the limiting factor. Published figures differ between sources, and koi clubs, breeders and food manufacturers each publish slightly different bands.
The feeding goal setting multiplies the band ration by 0.75 for maintenance and 1.25 for growth, within the same temperature band. Growth feeding assumes filtration and aeration that can absorb the additional waste; it is not a setting to use on a pond where ammonia or nitrite has ever read above zero.
Temperature conversions are exact (°C = (°F − 32) × 5/9) and weights convert at 1 oz = 28.3495 g and 1 lb = 453.592 g. Portion sizes are rounded for display only.
This calculator produces a feeding plan, not a health assessment. Fish that are off their food, losing condition or behaving abnormally need a diagnosis rather than a change of ration.