Grazing Days Calculator
The grazing days calculator tells you how many days a pasture or paddock can feed your livestock before the forage runs out, so you can plan rotations and move stock before the sward is overgrazed. The method is the standard forage-budget relationship every grazier uses: the number of grazing days equals the total available forage divided by the herd's total daily intake. Available forage is the dry matter standing above your target residual grazing height, measured in pounds, and total daily intake is the per-head intake multiplied by the number of head. Because grazing livestock eat roughly two and a half to three percent of their body weight in dry matter each day, a modest herd can clear a surprising amount of forage in a week. Enter your own available forage and daily intake to plan a rotation, decide when a paddock needs a rest, or check whether a block will carry the herd through a dry spell. Every figure here is computed deterministically from the formula shown in full below, with a worked example that reconciles exactly to the calculator so you can follow each step and trust the result rather than relying on a rough guess about how long a block will hold the herd.
Grazing days equals available forage divided by the herd's daily intake: days = available forage / daily intake. With 10,000 lb of available forage and a herd eating 400 lb/day, the paddock lasts 25.00 days. Larger herds shorten the grazing window.
Grazing days formula
Grazing days = F / I
F = available forage in pounds of dry matter
I = herd total daily intake in pounds of dry matter per day
Available forage is the dry matter above your residual grazing height. Daily intake is the per-head dry matter intake multiplied by the number of head. Dividing forage by intake gives the number of days the herd can graze the block.
Worked example
A paddock carries 10,000 pounds of available forage. The herd eats 400 pounds of dry matter a day.
- Available forage = 10,000 lb
- Daily intake = 400 lb/day
- Grazing days = 10,000 / 400 = 25
The paddock provides 25.00 grazing days. These are the calculator's default inputs, so the result above matches the widget exactly.
Grazing days at different intakes
Days from 10,000 pounds of available forage at a range of herd daily intakes.
| Available (lb) | Intake (lb/day) | Grazing days |
|---|---|---|
| 10,000 | 250 | 40.00 |
| 10,000 | 400 | 25.00 |
| 10,000 | 500 | 20.00 |
| 10,000 | 800 | 12.50 |
Land, water and resource data: US Geological Survey (USGS).
Grazing days calculator: frequently asked questions
What is grazing days?
Grazing days is how many days a pasture or paddock can feed a herd before the forage runs out. It is found by dividing the total available forage by the amount the herd eats each day. Graziers use it to plan rotations, decide when to move stock to a fresh paddock and avoid overgrazing, which damages the sward and slows regrowth.
How do I calculate grazing days?
Divide the total available forage (in pounds of dry matter) by the herd's total daily intake (in pounds of dry matter per day). If a paddock holds 10,000 pounds of available forage and the herd eats 400 pounds a day, it provides 25 grazing days. Available forage is usually the standing dry matter above a target residual grazing height, not the whole crop.
How much forage does a cow eat per day?
As a planning rule, grazing livestock consume dry matter equal to roughly 2.5 to 3 percent of their body weight each day. A 1,200 pound cow eats about 30 to 36 pounds of dry matter daily. Multiply the per-head intake by the number of head to get the herd's total daily intake, which is the figure this calculator divides into available forage.
What is a residual or grazing height?
The residual is the forage you intentionally leave behind so the pasture can recover quickly. Available forage is the dry matter above that residual height, not all the standing biomass. Grazing below the recommended residual slows regrowth, reduces root reserves and can thin the stand, so most rotational systems graze to a target residual and then move on.
Does this account for trampling and waste?
No. The basic formula assumes every pound of available forage is eaten. In practice animals trample, foul and refuse some forage, so utilisation is well below 100 percent. Continuous grazing may use only half the standing forage, while tight rotational grazing can reach 70 to 80 percent. Apply a utilisation factor to available forage before dividing if you want a more conservative figure.
Official sources
- Land, water and natural resource data: US Geological Survey (USGS). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.