Break-even flock size calculator

Where the starting figures come from

The feed-intake and laying-rate defaults are examples, not targets. They are not measurements of your flock, and they are meant to be replaced by your own records.

• Feed intake, 120 g per bird per day. UK guidance for an average adult hen is 100–120 g a day, so 120 g is the top of that band (British Hen Welfare Trust, Feeding your hens). A modern brown-egg hybrid holds a steady 100–105 g once mature, at a body weight of 1,700–1,800 g (Poultry Hub Australia, Nutrient requirements of egg laying chickens). Across small and backyard flocks the range is wider: 100–150 g (Alabama Cooperative Extension System, Feeding the Laying Hen, 2022). 120 g is within the UK and backyard ranges but above the cited 100–105 g hybrid range. Use measured intake for your breed and flock.
• Laying rate, 4.2 eggs per bird per week. That is about 218 eggs a year, near the centre of the published figures rather than the top of them. A small backyard flock should average 200–240 eggs per hen per year (UF/IFAS Extension, Raising Backyard Chickens for Eggs, publication AN239), and UK hens average 200–300 (RSPCA, Egg laying hens in UK farming). The FAO puts a typical bird at 208 eggs over twelve months, a weekly rate of four (Egg production, in Egg marketing: A guide for the production and sale of eggs). If your hens are retired commercial birds, as a great many UK flocks are, expect three or four eggs a week rather than more (British Hen Welfare Trust, How many eggs a day does a hen lay).

Every source gives a range, and none of them know your birds, your feed or your climate. This one matters more than the rest: on 35p of feed a bird a week, 4.2 eggs gives 8.3p per egg where 5 eggs gives 7.0p. Be careful about raising it without records to back it up.