Paddock Size Calculator

It converts your group's dry matter (DM) demand for a set occupation period, together with your pasture's pre-grazing cover and residual target, into the paddock area (in hectares and acres) needed to feed that group without overgrazing. It also works the other way: enter an existing paddock size and it tells you how many days that paddock will support the group.

No. This tool is built around the cattle/sheep dry-matter grazing-wedge method (AHDB's DMI percentages and pre-grazing cover/residual targets). Horse and pony paddock sizing depends more on exercise and welfare space than dry matter demand - use the Horse Paddock Size Calculator instead.

AHDB's rotational grazing guidance allocates 2.5% of liveweight per day to mature cows and 3% to calves and growing cattle - a 750kg cow eats about 18.5 kg DM/day on that basis. This calculator's presets use the same percentages against typical UK liveweights (700kg suckler cow, 350kg grower), and you can override either with the Custom option if you know your own herd's actual intake.

The presets scale from an AHDB-derived Farmers Weekly example: a 65kg ewe needs about 1 kg DM/day (1.5% of liveweight) in mid-pregnancy, rising to about 1.3 kg DM/day (2% of liveweight) in late pregnancy. This calculator applies the same percentages to a 75kg ewe default. Ewes with lambs at foot in peak lactation eat considerably more than either pregnancy figure - use Custom and your own known intake for that group.

Pre-grazing cover is how much dry matter is standing in the paddock before animals go in, usually measured with a plate meter or sward stick. AHDB's guidance targets 2,700-3,200 kg DM/ha for maximum grazing performance; cover below that often means the paddock hasn't rested long enough, and cover well above it usually means the grass has gone stemmy and would suit silage better than grazing.

Residual is the dry matter left standing once the group moves off. AHDB's rotational grazing target is around 1,500 kg DM/ha: leaving less than that risks damaging the sward's regrowth (overgrazing), and leaving significantly more wastes grass that goes uneaten.

There's no single right answer, but shorter occupation periods (roughly 1-4 days) generally improve grass utilisation and, for sheep, help control worm burdens, since guidance puts the worm-egg-to-infective-larvae window at 4-10 days. Longer occupation periods (a week or more) are simpler to manage but move closer to set-stocking, with the utilisation and parasite-control benefits of rotational grazing reduced accordingly.

Roughly: (rest period in days / occupation period in days) + 1. A 30-day rest with a 3-day occupation needs about 11 paddocks; the same 30-day rest with a 7-day occupation needs about 5, though each paddock is grazed harder before the group moves on with fewer, longer stays.

It can be one tool among several. Guidance from Farming Connect notes that moving sheep off a paddock inside the 4-10 day window before worm eggs become infective larvae, then resting that paddock for 30-60 days, allows over 90% of larvae to die off before sheep return. It is not a substitute for faecal egg counts or a vet-led worm control programme - see your vet or SCOPS guidance for a full programme.

A plate meter or sward stick gives the most reliable figure, but as a rough guide, grass at typical mid-rotation grazing height (10-15cm) in good UK growing conditions is often in the 2,500-3,000 kg DM/ha range. If you are unsure, entering a lower, more conservative cover estimate is safer than overestimating, since overestimating cover leads to undersized paddocks and unplanned overgrazing.

No. The calculator works from the cover and residual figures you enter; it does not adjust for weather risk, ground damage from stock traffic in wet conditions, or drought-stressed grass that may look present but has little feed value. Adjust your own cover estimate downward in those conditions rather than relying on a seasonal default.

Either - the calculator shows both, and the optional existing-paddock field accepts whichever unit you prefer. 1 hectare = 2.47105 acres. UK land is measured in hectares in most official agricultural guidance (including AHDB's), but many smaller holdings and rural listings still use acres.

Yes - the same demand-divided-by-grazable-dry-matter formula applies whether the occupation period is half a day or a week; just set the Occupation Period input to whatever your system actually uses. Very short, very high-density mob grazing typically also uses a higher target residual than the 1,500 kg DM/ha default, so adjust that input if your system specifies one.

Because UK grass growth rate itself changes through the season - roughly a 4-to-1 swing between March and the May/June peak - a cover reading and paddock size that were right three weeks ago may no longer be right. Most rotational grazers re-walk and re-measure cover weekly, or before every paddock move if growth is changing quickly.

Yes, using the Dairy Cows At Grass preset, which applies the same 3% of liveweight used for growing cattle rather than the lower 2.5% cow rate, as a cautious allowance for the extra intake lactation demands. High-yielding dairy cows on very good pasture can still eat more than this preset assumes - use Custom with your own known intake figure if you have one.

No. This tool gives a planning estimate from the dry matter intake and grazing targets you enter. It does not replace measuring your own pasture with a plate meter or sward stick, and it is not agronomic, veterinary, or animal welfare advice.