Humid Hide & Shed Box Calculator
Size a humid hide and work out exactly how much moist substrate and water it needs to hold the right humidity for healthy, complete sheds — without flooding the box.
Box & Substrate Planner
Enter your animal and container details. Results assume real-world evaporation and substrate behaviour.
Enter a length between 1 and 400.
Enter a humidity between 50 and 100%.
Enter a whole number of days between 1 and 14.
Recommended box footprint
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Full breakdown
Overview
A humid hide is a small enclosed box inside a reptile enclosure, packed with moist substrate, that gives an animal a pocket of high humidity to retreat into. It is the single most reliable tool for preventing incomplete or "stuck" sheds in snakes, geckos, and many lizards, and it doubles as a calm, dark refuge that reduces stress.
This calculator is built for keepers who want to get the box right the first time rather than guessing. It sizes the hide to the animal so the box is snug enough to feel secure but large enough to turn around in, then works out how much substrate and water that volume actually needs — accounting for real-world evaporation and how different substrates hold moisture. Whether you keep a single ball python or a rack of geckos, it turns husbandry rules of thumb into concrete numbers.
How It Works
- Enter your animal's length (snout to tail tip) and pick the unit. The hide footprint is sized from this so the animal can curl up fully inside.
- Choose your substrate. Each option carries a realistic depth and a moisture-retention factor, because sphagnum holds far more water than cypress mulch.
- Set your target humidity inside the hide (most species do well at 70–90% during a shed cycle).
- Tell it how often you'll re-moisten the box. Longer gaps need more starting water to survive evaporation.
- Press Calculate. You get a recommended box size plus a full breakdown of substrate volume and the exact water to add now and at each top-up.
Formula Explanation
The box is sized so the animal can coil inside a circle roughly one-third of its body length across. That diameter sets the footprint:
Box side ≈ animal length × 0.35Floor area = side × side
Substrate volume is the floor area times a substrate-specific depth. To keep small boxes usable, the depth is capped so it never exceeds about a third of the box side (with a 3 cm floor), leaving air space above the bedding:
Depth = min(ideal depth, max(3 cm, box side ÷ 3))Substrate volume = floor area × depth
Water is the part most guides skip. We start from the volume of water the damp substrate should hold at your target humidity, then add an evaporation allowance based on how long the box sits between top-ups:
Hold water = volume × retention × 0.18 × (humidity − 50) ÷ 50Evaporation = floor area × 0.04 mL/cm²/day × daysWater now = Hold water + Evaporation
The 0.18 mL/cm³ figure reflects substrate that is damp like a wrung-out sponge rather than saturated, and the (humidity − 50) ÷ 50 term scales water up only as your target rises above the 50% baseline. The per-cycle top-up equals the evaporation portion alone, since the substrate's held water stays in the box between refreshes.
Practical Benefits
- Fewer stuck sheds. Correct humidity in a dedicated hide is the most cited fix for retained eye caps and tail-tip shed in keeper communities.
- No guesswork on water. Knowing the exact mL to add stops the two most common mistakes — a bone-dry box or a swampy one that breeds scale rot and mould.
- Right-sized boxes. A hide that's too big won't feel secure; too small and the animal can't use it. The footprint math gets it in the goldilocks zone.
- Cheaper restocking. Buying substrate by calculated volume avoids over-purchasing and waste, useful when running multiple enclosures or a breeding rack.
- Repeatable routine. A fixed top-up schedule with a known water amount makes care predictable for you, pet-sitters, or a shared collection.
