Grazing Days Calculator

Frequently Asked Questions

How do I measure standing forage?

Clip and weigh a known area (e.g., 1 sq ft), dry the sample completely, and multiply by your paddock area. Alternatively, use a rising-plate meter calibrated to your pasture type, or contact your local extension service for regional forage production estimates by soil type and rainfall.

Why limit days per paddock?

Short grazes followed by long rests let plants rebuild root reserves and leaf area, the engine of a productive rotation. Overgrazing removes too much leaf material, depriving the plant of photosynthetic capacity and slowing regrowth. A general rule is to move animals when forage has been grazed to 3-4 inches residual height.

What utilization rate is realistic?

Around 50% for managed rotation, lower under continuous grazing or in drought, higher only with very frequent moves and careful monitoring. Exceeding 60-65% routinely under continuous grazing will thin the stand over seasons.

Does class of stock matter?

Yes - growing, lactating, or larger animals eat more than the 2.6% default suggests. Adjust the intake percentage upward for nursing cows (3.0-3.5%), growing yearlings (2.5-3.0%), or horses (1.5-2.0%). Downward adjustments apply for older, idle, or lighter animals.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Rotational grazing lives or dies on one question: how many days can this paddock feed this herd before they need to move? This calculator answers it by comparing supply against demand. On the supply side it takes the available forage - pasture acres times pounds of dry matter per acre, scaled by a utilization factor because cattle never harvest every blade. On the demand side it computes the herd's daily appetite as head count times average weight times the percentage of body weight eaten per day (about 2.6% of dry matter for a grazing animal). Dividing usable forage by daily demand gives the number of grazing days, the figure that drives your move dates, paddock sizing, and rest periods in a managed rotation.

Formula and Method

Daily herd intake (lb DM) = herd size × average weight (lb) × (intake % ÷ 100). Total available forage (lb DM) = acres × forage (lb DM/acre) × (utilization % ÷ 100). Grazing days = total available forage ÷ daily herd intake. The default intake is 2.6% of body weight and the default utilization 50%; both are editable. Forage should be the dry-matter yield standing in the paddock now, not the annual total. All quantities must be positive and the percentages within sensible bounds.

Worked Example

A 20-acre paddock carrying 3,000 lb DM per acre, grazed at 50% utilization, with 25 cows averaging 1,200 lb eating 2.6% of body weight daily. Daily herd intake = 25 × 1,200 × 0.026 = 780 lb. Total available forage = 20 × 3,000 × 0.50 = 30,000 lb. Grazing days = 30,000 ÷ 780 ≈ 38 days. That is long for a single paddock - most rotations subdivide so the herd stays a few days and the grass gets a long rest, so you might split this into eight or nine moves.

Planning a Rotation

The grazing days figure from this calculator is the capacity for the whole paddock. In practice, most rotational systems aim for a short graze (3-7 days per paddock) followed by a long rest (21-60 days) to allow full root and leaf recovery. To plan a rotation, divide the total grazing days by your target days-per-paddock to find the number of paddocks needed.

For example: 38 grazing days ÷ 4 days per paddock = about 9-10 paddocks to keep the herd moving and the resting paddocks recovering. Use temporary electric fence and a reliable water source in every paddock to make moves easy and keep the cattle content.

Common Mistakes

Entering annual forage production instead of the dry matter actually standing in the paddock right now.

Overstating utilization - leaving too little residual stunts regrowth and lengthens the rest period you need.

Forgetting that forage regrows during a long graze, so very long stays under-count true capacity but overgraze the plants.

Using as-fed weight against a dry-matter forage estimate, mismatching the moisture basis on the two sides.

Ignoring trampling and fouling losses, which rise sharply when a herd lingers past a few days on one paddock.

Grazing Days Calculator

Frequently Asked Questions

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