Question 1

How do I calculate how much drench I need for my sheep?

Accepted Answer

To calculate drench volume: divide the animal's liveweight by the "per kg" figure on the label, then multiply by the "ml per" figure. For example, at 1 ml per 10 kg, a 50 kg sheep needs (50 ÷ 10) × 1 = 5 ml. Multiply by your head count to get the total volume needed, then add 5% for wastage, and round up to the nearest full bottle. This calculator does all of that automatically — enter your dose rate from the label and your group details.

Question 2

What pack size do I need to drench 100 sheep?

Accepted Answer

It depends on the dose rate and average weight of your sheep. At 1 ml per 10 kg and an average weight of 60 kg, each sheep needs 6 ml. 100 sheep × 6 ml = 600 ml total, plus 5% wastage = 630 ml. A 1-litre bottle is sufficient. At a higher dose rate or heavier sheep, you may need a 2.5-litre bottle. Use the calculator above — enter your specific dose rate from the product label and your sheep's average weight.

Question 3

Why should I weigh my livestock before dosing?

Accepted Answer

Dose rates for veterinary medicines are based on liveweight. Under-dosing — giving less than the label dose because you underestimated weight — is a leading cause of anthelmintic (wormer) resistance development. Sub-therapeutic doses kill susceptible worms but allow resistant worms to survive and reproduce, passing on resistance. Over-dosing wastes money and can occasionally cause adverse reactions. Weighing at least a sample of your animals before dosing gives a reliable average for the whole group.

Question 4

Can I use this calculator for cattle injections?

Accepted Answer

Yes — the calculator works for any veterinary medicine where the dose rate is expressed as a volume per unit of liveweight, regardless of administration route. Enter the dose rate from the label (e.g. 1 ml per 50 kg for some injectable products), your cattle's average weight and head count, and the calculator gives you the total volume and bottles to order. Always check the label for the correct administration route, injection site, and needle size.

Question 5

What is a withdrawal period and how do I find it?

Accepted Answer

A withdrawal period is the minimum time that must elapse between administering a veterinary medicine and slaughtering the animal for meat, or using the milk for human consumption. It is stated on the product label and packaging. You must record the withdrawal period in your medicine records and ensure animals are not sent to slaughter or milked during the withdrawal period. Withdrawal periods vary enormously between products — always check the label for the specific product you are using.

Question 6

How do I record livestock medicine use for farm assurance?

Accepted Answer

UK farm assurance schemes (Red Tractor, QMS, RSPCA Assured etc.) require medicine records that include: product name and batch number, date of purchase and administration, withdrawal period, animals treated, dose administered, and name of person who administered it and the prescribing vet or SQP. Records must be kept for at least 5 years. This calculator generates a PDF formatted to meet these requirements — complete all the optional fields before downloading for a full record.

Question 7

What is an SQP and why do I need one for some medicines?

Accepted Answer

An SQP (Suitably Qualified Person) is a specially trained animal medicines advisor, usually at an agricultural merchant or veterinary practice. In the UK, veterinary medicines classified as POM-VPS (Prescription Only Medicine — Veterinarian, Pharmacist or Suitably Qualified Person) can only be supplied by a vet, pharmacist or SQP. Most farm anthelmintics (wormers) and many other routinely used farm medicines are POM-VPS. You do not need a vet prescription for POM-VPS medicines but you do need to obtain them from a registered supplier.

Question 8

How much wastage should I allow when ordering drench?

Accepted Answer

A 5% wastage allowance is standard for automatic refilling drench guns in good working order. Add more for: large groups dosed quickly (some animals resist and get partial doses), pour-on products applied in windy conditions, older or poorly calibrated equipment, or when priming a large volume gun. Set wastage to 0% to see the minimum theoretical requirement, but always order with at least 5% buffer to avoid running short mid-job.

Livestock Dosing Calculator

Product & Dose Rate

Animal Groups

How to Use This Calculator

Why Accurate Weighing Matters

Medicine Record Keeping — Legal Requirements

Frequently Asked Questions