Lambing Calculator.
Work out when your ewes are due to lamb. Enter the date the ram went in (tupping) or the mating date, and the calculator gives the expected lambing date based on a 147-day gestation. Add a ram-out date to see the full lambing spread for the flock.
How to use this calculator
- Enter the date the ram went in (tupping).
- Add a ram-out date to see the full lambing spread.
- Choose 147, 145 or 150 day gestation.
- Click calculate to get your expected lambing date.
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Never miss a lambing date again
Herdwatch records tupping, scanning and lambing for your whole flock, and sends due-date reminders straight to your phone. Trusted by over 100,000 farmers.
- Tupping, scanning and lambing records in one place
- Due-date reminders sent straight to your phone
- Flock records ready for inspection
Understanding ewe gestation in Ireland
A ewe's gestation length is the number of days from mating to lambing. The average is 147 days, or about five months, with most ewes lambing between 142 and 152 days. Actual length varies a little by breed, by litter size and by the condition of the ewe.
To plan a lambing start date, count back 147 days from the date you want to start lambing, and put the ram in then. For example, for lambing to start on 1 March, the ram should go in around 5 October.
| Stage | Timing | Notes |
|---|---|---|
| Ram in (tupping) | Day 0 | Raddle or harness helps you record service dates |
| Scanning | About day 80 to 90 | Confirms singles, twins and triplets |
| Increase feed | 6 to 8 weeks pre-lambing | Ewes need higher-protein concentrates late in pregnancy |
| Lambing | Around day 147 | Range about 142 to 152 days |
Source: Teagasc and Agri Aware. The mean gestation length in sheep is 147 days. Individual ewes may lamb a few days either side.
Tips for a smooth lambing season
- Use a raddle harness and change the colour every cycle so you can group ewes by service date.
- Batch ewes by expected lambing date to make feeding and supervision easier.
- Lift ewe nutrition in the last 6 to 8 weeks so lambs are strong and colostrum is plentiful.
- Have your lambing kit and vet's number ready before the first ewe is due.
Flock records that keep you compliant.
Herdwatch tracks breeding, medicines and flock movements, and helps with compliance. Request a quote and we will set you up for your flock.
Frequently asked questions
About 147 days, or roughly five months. Most ewes lamb between 142 and 152 days after mating, depending on breed, litter size and condition.
Count back 147 days from your target lambing start. For lambing to begin on 1 March, put the ram in around 5 October.
It uses the 147-day average gestation, so it gives a reliable target date. Individual ewes can lamb a few days before or after, and ewes carrying multiples often lamb slightly earlier.
This tool works from one tupping date at a time. The Herdwatch app records service and lambing dates for every ewe and reminds you as each is due.