Ovulation rate
More eggs shed means more twins. Breed, ewe age and body condition at joining set it, and flushing thin ewes before the ram goes in can lift it.
Breeding & Reproduction
Lambing Percentage Calculator
Enter the ewes put to the ram, the ewes that lambed and the lambs born. The calculator returns your lambing percentage, the average litter size and, if you add the lambs weaned, your weaning percentage. These are the headline numbers most flocks are judged on.
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Your result
Lambing Percentage Calculator result
Lambing percentage160%
A strong lowland result, with most ewes rearing twins.
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Estimates for planning only. Results depend on the figures you enter and on typical published values, and real animals and farms vary. Consult a qualified veterinarian, nutritionist or adviser before making animal health, feeding or financial decisions.
The breakdown
Updates as you type- Lambs per ewe lambed
- 1.7
- Ewes that lambed
- 94%
- Ewes that did not lamb
- 6
- Weaning percentage
- 148%
- Lambs lost before weaning
- 12
The basics
What Is Lambing Percentage?
Lambing percentage is the number of lambs born for every 100 ewes put to the ram. A flock that joins 100 ewes and lambs 160 lambs has a 160% lambing percentage. Scanning percentage counts foetuses at ultrasound, lambing percentage counts lambs born and weaning percentage counts lambs alive at weaning.
The Lambing Percentage Calculator divides lambs born by ewes joined and multiplies by 100. The calculator returns litter size and weaning percentage from the same flock records. Prolific breeds such as Finnsheep and Romanov exceed 200%, and hill breeds such as Scottish Blackface and Welsh Mountain run between 90 and 130%.
What the Lambing Percentage Calculator Calculates
The Lambing Percentage Calculator returns 4 results:
- Lambing percentage: lambs born per 100 ewes joined
- Litter size: lambs born per ewe that lambed
- Ewes lambed: the percentage of joined ewes that produced a lamb
- Weaning percentage: lambs weaned per 100 ewes joined
When to Use the Lambing Percentage Calculator
There are 3 main uses for the Lambing Percentage Calculator:
- Benchmark the lamb crop after lambing ends
- Compare seasons, sire groups or ewe age classes
- Set targets for flushing, scanning and lamb survival
Getting started
How to Use the Lambing Percentage Calculator
To use the Lambing Percentage Calculator, follow 3 steps: start with ewes put to the ram, then add ewes lambed and lambs born, then add lambs weaned if you have it. The result updates as you type.
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Step 1: Start with ewes put to the ram
Ewes put to the ram is the fairest base. It keeps empty ewes in the sum instead of quietly dropping them.
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Step 2: Add ewes lambed and lambs born
Count every lamb born, alive or dead, so the figure reflects what the ewes actually produced.
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Step 3: Add lambs weaned if you have it
Weaning percentage shows what reached sale or selection, which is the number that pays the bills.
The maths
Lambing Percentage Formula
Lambing percentage is lambs born for every 100 ewes joined.
Lambing percentage = Lambs born ÷ Ewes put to the ram × 100
Some people divide by ewes lambed instead, which always gives a higher number. Say which base you used when you compare figures with another flock.
Worked example
- Ewes put to the ram 100
- Lambs born 160
- Lambing percentage 160 ÷ 100 × 100 = 160%
- Litter size 160 ÷ 94 ewes lambed = 1.70
Reference
Typical Lambing Percentages by System
Lambs born per 100 ewes joined in common flock types.
| Flock type | Lambing percentage |
|---|---|
| Hill, range and fine-wool flocks | 90 to 130% |
| Upland and crossbred flocks | 130 to 160% |
| Lowland meat flocks | 150 to 190% |
| Prolific breeds such as Finnsheep and Romanov crosses | 200% and above |
Typical ranges only. Breed, ewe age, body condition at joining and the season all move the figure.
Glossary
Lambing Percentage Terms Explained
6 terms appear in the Lambing Percentage Calculator and in the guidance around it.
Scanning percentage
- Scanning percentage is foetuses counted per 100 ewes joined, measured at ultrasound 45 to 90 days after mating.
Marking percentage
- Marking percentage is the Australian and New Zealand measure: lambs alive at marking (tailing) per 100 ewes joined. Merino flocks commonly mark 80 to 100%.
Weaning percentage (weaning rate)
- Weaning percentage, or weaning rate, is lambs alive at weaning per 100 ewes joined.
Litter size (prolificacy)
- Litter size, or prolificacy, is lambs born per ewe that lambed. A flock with equal numbers of singles and twins has a litter size of 1.5.
Ovulation rate
- Ovulation rate is the number of eggs a ewe sheds per oestrous cycle. Ovulation rate sets the upper limit on litter size.
Flushing
- Flushing is a rising plane of nutrition for 2 to 3 weeks before joining. Flushing lifts ovulation rate in thin ewes.
Good to know
What Moves Lambing Percentage
3 factors move lambing percentage: ovulation rate, empty ewes and lamb losses around birth.
Empty ewes
Every empty ewe counts as zero lambs. A five-point drop in conception rate takes a similar bite out of your lambing percentage.
Losses around birth
Lambs born dead or lost in the first days come straight off the weaning figure. Shelter, colostrum and a well-fed ewe in late pregnancy protect it.
Answers
Frequently Asked Questions
Common questions about the lambing percentage calculator and the numbers behind it.
What is a good lambing percentage?
It depends on the system. Around 150 to 190% is a common target for lowland meat flocks, while hill and extensive flocks often work at 90 to 130%. The best figure is the one your land and labour can rear well.
How do you calculate lambing percentage?
Divide the number of lambs born by the number of ewes put to the ram and multiply by 100. For example, 160 lambs from 100 ewes is a 160% lambing percentage.
What is the difference between lambing percentage and weaning percentage?
Lambing percentage counts lambs born. Weaning percentage counts lambs still alive at weaning, per 100 ewes joined. The gap between the two is your lamb loss.
Can lambing percentage be over 200%?
Yes. Prolific breeds such as Finnsheep and Romanov, and their crosses, regularly average more than two lambs per ewe. Rearing that many well takes more feed and more labour at lambing.
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