The right feeder size, the right prey weight, and the right supplement — worked out for your species rather than for reptiles in general, because a leopard gecko and a sulcata have almost nothing in common at dinner time.
Last reviewed August 2026 · Free · Nothing you enter is stored
The standard feeder size rule is that no prey item should be wider than the space between the animal's eyes. It is the first thing anyone is told and it is repeated in every care sheet in the hobby.
It is directionally sound. Oversized prey is a documented cause of regurgitation and of impaction, and both are serious, so a conservative ceiling on feeder width is genuinely useful. What it is not is a measured threshold. The rule traces to keeper consensus rather than to any published study, and nobody has established that a feeder one millimetre over the line causes harm while one millimetre under it does not.
The honest way to use it is as a safe upper bound rather than a target. If you are choosing between two sizes, take the smaller. Two appropriately sized insects are better food than one that the animal has to work at.
Prey for a ball python should weigh 10 to 15 percent of the snake's body weight. That is the figure to work from, and it is why a kitchen scale is a more useful purchase than most of what gets sold alongside a snake.
Corn snakes are handled slightly differently because they are often given more than one item at a sitting. The combined weight of everything fed at once should stay near 10 percent of body weight, and prey width should be one to one and a half times the snake's widest point. Width decides whether a meal goes down without trouble; weight decides whether the animal is being overfed across a year.
Obesity in captive snakes is common and is nearly always the result of feeding a schedule rather than an animal. Enter a weight in grams above and the tool gives you the prey range in grams, which is how frozen prey is sold anyway.
Body condition is a better guide than any interval. A snake that is holding weight, alert, and not showing a prominent spine is being fed enough, whatever the care sheet says about every seven days.
This matters most with ball pythons, which fast seasonally. An adult refusing food for weeks through the winter is usually behaving exactly as the species behaves, and wild adult ball pythons eat roughly ten times a year, which puts a run of refused meals into proportion. Weigh the animal, write the number down, and worry about the trend rather than the individual meal.
Refusal that comes with weight loss, a change in behaviour, or any other symptom is a different matter and warrants a reptile vet. So does regurgitation, which is often the first sign that prey has been too large or the enclosure too cold to digest it.
A live rodent is an animal with teeth that has been put in a box with a predator that may not be hungry. Rats in particular can inflict serious injuries on a snake that is not interested in eating, and because feeding is usually left to happen quietly, the damage is generally discovered rather than witnessed.
Frozen-thawed prey removes that risk entirely, removes the parasite risk that comes with live rodents, and has the practical advantage of being sold by weight, so you can buy exactly the size the calculation above asks for. Thaw in the refrigerator and warm to body temperature in a sealed bag in warm water rather than in a microwave.
Diet type and feeding interval change more between reptile species than almost anything else in their care. These are the schedules the tool works from:
| Species | Diet | Feeding |
|---|---|---|
| Bearded Dragon | Insectivore | Adults: 3-4 head-sized portions of insects twice a week, salad most days. Juveniles: insects daily, as much as eaten in ten minutes. |
| Leopard Gecko | Insectivore | Juveniles daily — two appropriately sized insects per inch of body length. Young adults every two to three days, mature adults every five. |
| Crested Gecko | Omnivore | Prepared crested gecko diet three times a week, with appropriately sized insects once or twice a week as enrichment. |
| Gargoyle Gecko | Omnivore | Prepared diet three times a week plus insects once or twice weekly. |
| Ball Python | Rodent eater | Feed by body condition rather than by calendar. Prey should weigh 10 to 15 percent of the snake's body weight. Wild adults eat roughly ten times a year. |
| Corn Snake | Rodent eater | Hatchlings every 5 to 7 days, juveniles every 7 to 10, adults every two to three weeks. Combined prey weight should stay near 10 percent of body weight. |
| Kingsnake / Milk Snake | Rodent eater | Every 7 to 14 days depending on age and body condition, prey around 10 percent of body weight. |
| Blue-Tongue Skink | Omnivore | Adults twice a week: roughly 50 percent protein, 40 percent vegetables, 10 percent fruit. Juveniles every other day. |
| Green Anole | Insectivore | Two to four appropriately sized insects daily for adults, dusted with calcium. |
| Veiled Chameleon | Insectivore | Adults every other day, 8 to 12 insects. Juveniles daily. |
| Panther Chameleon | Insectivore | Adults every other day, 8 to 12 insects. Juveniles daily. |
| Red-Eared Slider | Omnivore | Adults every other day, mostly greens with a small amount of protein. Juveniles daily. |
| Ornate Box Turtle | Omnivore | Adults every other day: insects, greens and a little fruit. Juveniles daily. |
| Russian Tortoise | Herbivore | Daily weeds and leafy greens. No fruit, no commercial pellets as a staple, and never dog or cat food. |
| Hermann's Tortoise | Herbivore | Daily weeds and leafy greens, high fibre and low protein. |
| Sulcata Tortoise | Herbivore | Grass and hay as the overwhelming majority of the diet. Grazing, not bowl feeding. |
Prey weight as a percentage of the snake's body weight follows ReptiFiles: 10 to 15 percent for ball pythons, and for corn snakes a combined weight not exceeding about 10 percent when several items are fed at once. Feeding by body condition beats feeding by calendar for every snake species.
Calcium goes on every feeding. Whether it should contain D3 depends entirely on your lighting. An animal under a working UVB lamp is already producing vitamin D and should be given calcium without D3, because dietary D3 substitutes for what UVB provides and oversupplying it is its own problem. An animal with no UVB should be given calcium with D3, since that is then its only route — though fitting proper UVB is the better answer, and our UVB calculator works out the lamp and distance. A multivitamin goes on roughly once a week in either arrangement.
None of that fixes a monotonous diet. A single feeder species is deficient food whatever you dust it with, because dusting corrects minerals and leaves everything else where it was. Rotate at least three feeders, and gut-load them for 24 hours before they go in — an insect that has eaten well in the last day is materially different food from one that has been sitting in a shipping tub.
| Feeder | Rough size | Role in the diet |
|---|---|---|
| Dubia roach | Quarter-inch nymph up to an inch and a half adult | A staple. Sold across a wide size range, so you can match the animal rather than whatever the shop had in. Softer bodied than a mealworm and taken readily by most insectivores. |
| Banded cricket | Pinhead up to around three quarters of an inch | A staple, and the easiest feeder to buy small enough for hatchlings. Hardier and quieter in the tub than the brown house cricket it has largely replaced. |
| Black soldier fly larva | Around half to three quarters of an inch | Unusually calcium-rich — the one common feeder that carries meaningful calcium in its own body rather than relying entirely on what you dust onto it. Still worth dusting for a growing animal. |
| Mealworm | Around an inch | A treat rather than a staple. The shell is hard relative to the meat inside and the fat content is high for something fed routinely. |
| Superworm | Around two inches | Occasional rather than routine, for the same reasons as the mealworm, and at a size that suits only the larger lizards. |
| Hornworm | Half an inch to three inches as it grows | Very high in moisture, which makes it useful for hydration and for tempting an animal that has gone off its food. Too watery to build a diet on, and it grows fast enough to outsize a small lizard within days. |
| Waxworm | Around an inch | A treat only. Very high in fat, taken enthusiastically to the exclusion of better food, and comfortably the feeder most often overused. |
No wider than the space between the animal's eyes. That is the rule the whole hobby runs on, and it is a sensible ceiling — oversized prey is a documented cause of regurgitation and impaction. It is worth being honest about where it comes from, though. It traces to keeper consensus rather than to any published study, so treat it as a safe upper bound rather than a measured threshold. If you are between two sizes, take the smaller one.
By weight, not by eye. Prey should weigh 10 to 15 percent of a ball python's body weight. For a corn snake, the combined weight of everything fed at one sitting should stay near 10 percent, and prey width should be one to one and a half times the snake's widest point. Width is the dimension that decides whether a meal goes down comfortably; weight is the one that decides whether the snake is being overfed across a year.
Usually because it is a ball python in winter. Seasonal fasting is normal behaviour for the species, and wild adults eat roughly ten times a year, which puts a few refused meals in perspective. Feed by body condition rather than by calendar: if the spine is not becoming prominent and the animal is alert and holding weight, a refused meal is information, not an emergency. Persistent weight loss, a change in behaviour, or refusal alongside any other symptom is a vet visit.
Frozen-thawed only. A live rodent is a rodent with teeth, and a snake that is not hungry will not defend itself. Rats can badly injure or kill a snake, and it almost always happens while nobody is watching. Frozen-thawed also removes the parasite risk and lets you buy prey in the exact weight the animal needs.
Calcium on every feeding either way. Use calcium without D3 if the animal has working UVB, because it is already making its own vitamin D and adding more on top is its own problem. Use calcium with D3 if it does not have UVB, because dietary D3 is then the only route it has. Add a multivitamin roughly once a week. Providing proper UVB and dusting without D3 is the better arrangement of the two.
No. A single feeder species is a deficient diet whatever you dust it with, because dusting corrects minerals and does nothing about the rest of the nutritional profile. Rotate at least three feeders, and gut-load them for 24 hours before they go in — an insect that has eaten well in the last day is a different food from one that has been sitting in a tub since it was shipped.
