Hay is the food guinea pigs must never run out of, and buying enough of it is a monthly maths problem. Pigs eat a large pile every day, waste a fair amount as bedding, and go through bags far faster than new owners expect. This free hay calculator turns your herd size into kilos eaten per month, kilos to buy per month with waste included, kilos per week, and nine kilo bales per month, so you can order with confidence.
Unlimited hay matters for two reasons that both need daily fibre. First, guinea pig teeth grow all through life, and only constant chewing on long fibre wears them down evenly. Second, the gut needs fibre moving through it at all times, and a gut without hay slows down, which can turn into bloat or stasis, both emergencies. Hay is not a side dish for guinea pigs, it is the main food.
Using the calculator is simple. Enter how many guinea pigs you have and press Calculate hay. The result shows kilos eaten per month at about three kilos per pig, kilos to buy per month at about four kilos per pig once waste is included, the weekly buy amount, and how many nine kilo bales that means. Two pigs therefore need about six kilos eaten and eight kilos bought each month, or about one nine kilo bale.
A worked example helps with ordering. Four pigs eat about twelve kilos per month and need about sixteen kilos bought, which is two nine kilo bales. Buying in bales is usually cheaper per kilo than small bags, and it suits herds of two or more. A single pig household may do better with small fresh bags, since a bale stored for months loses freshness and picks up dust.
Hay types suit different pigs. Timothy hay is the standard adult hay, with a good balance of fibre and protein. Meadow hay is softer and suits fussy pigs, while oat hay adds variety and crunch. Alfalfa hay is rich in calcium and suits young, pregnant, or nursing pigs, but it is too rich for healthy adults long term. Rotate types if your pigs get bored, but always keep one type they reliably eat.
Waste is normal and can be reduced, but not removed. Pigs pull hay from racks, trample it, toilet on it, and then refuse the soiled pile, which is natural behaviour, not fussiness. A hay rack or hay bag over a litter area catches much of the waste where it can be cleared easily, and refilling little and often keeps hay fresh and appealing. Soiled hay should be removed daily, since damp hay grows mould.
Storage decides whether bought hay stays good. Keep hay dry, cool, and ventilated, never in a sealed plastic bag where damp collects, and never in direct sun. A cardboard box or a fabric bale bag in a dry room works well. Check each new pile for dust, mould, or a sour smell, and throw away any suspect hay, since mouldy hay can cause breathing problems and gut upsets in guinea pigs.
Ordering on a schedule beats ordering when the bag runs out, because hay shortages stress pigs and owners alike. Set a repeat order or a calendar reminder based on the monthly buy number from this calculator, and order when you still have one week of hay left, not when the last pile is gone. Delivery delays happen, and a week of buffer turns a late parcel into a minor annoyance instead of an emergency. If you buy bales, open one bale at a time and keep the rest sealed and dry, since an open bale loses freshness faster. A steady hay supply is the cheapest health insurance a guinea pig owner can buy, and this calculator gives you the number to plan around.