Forage allowance calculator
Compare grazing pressure fairly across paddocks and herds: 6800 kg of usable dry matter on 4 ha for 40 animals of 450 kg means 18000 kg of live weight to feed and 170 kg of forage per animal. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Herbage mass
- 2,500
- Area
- 4
- Animal count
- 40
- Live weight
- 450
- Residual mass
- 800
- Available density kg ha
- 1,700
- Area unit
- hectare
- Area hectares
- 4
- Area acres
- 9.8842152587
Forage allowance is a core grazing-management ratio: how much standing or allocated forage dry matter is available for each kilogram of animal live weight on a paddock. Ranchers, dairy graziers, sheep and goat managers, and range scientists use it to compare stocking pressure across fields of different size and herds of different weight without collapsing everything into a single head-count. This forage allowance calculator takes herbage mass in kilograms of dry matter per hectare, paddock area in hectares or acres, animal head count, mean live weight in kilograms, and an optional residual mass you intend to leave after the graze. It returns available forage mass, total live weight, forage allowance in kg DM per kg live weight and per 100 kg live weight, forage per animal, and stocking rates.
What forage allowance means and how it is calculated
Forage allowance links the mass of edible herbage on offer to the metabolic and structural size of the herd that will graze it. Unlike a raw stocking rate of animals per hectare, it normalizes for live weight so forty lightweight yearlings are not treated the same as forty mature cows. Available forage is the product of available herbage density and paddock area in hectares.
Available density is the standing herbage mass density minus an optional residual mass you choose to leave for regrowth, soil cover, or animal welfare—never less than zero. Herbage mass is entered as kilograms of dry matter per hectare, the unit soil- and pasture-sampling crews report after clipping, drying, and scaling to area. Area may be given in hectares or acres; acres convert with the international-foot factor so results stay comparable across regions that still measure paddocks in acres.
Total live weight is animal count times mean live weight per head. The calculator also multiplies forage allowance by one hundred to report kilograms of dry matter per one hundred kilograms of live weight, a pastoral reporting convention used in many extension bulletins, and it reports forage per animal and head per hectare or per acre for context.
Interpret the ratio with local targets: high allowance can mean under-utilized pasture or generous allocation for high performance; low allowance can mean tight residual risk, reduced intake, or a need to reduce stock or open more area. This tool is a transparent first-order planning metric, not a substitute for on-farm pasture measurement protocols or veterinary nutrition plans.
Where a forage allowance calculator earns its keep
Rotational and strip-grazing planners need a fast way to turn a rising-plate meter or cut-and-dry sample into a stocking decision before the next move. Extension educators and classroom labs teach that head per hectare alone misleads when animal classes differ, and forage allowance makes that lesson concrete with numbers students can re-run. Consultants comparing two client paddocks—one large with heavy cows, one small with lambs—need a shared metric in kilograms per kilogram or per one hundred kilograms of live weight.
Use residual mass deliberately when your protocol leaves a measured residual height or mass; set it to zero only when the entire standing crop is considered available.
What you can do with it
Plan the next rotational graze from a pasture sample
Enter clipped herbage mass, paddock area, head count, and mean live weight to get forage allowance and available kilograms before you open the next break.
Compare stocking pressure across herds of different weight
Normalize two paddocks by live weight so heavy cows and lighter stockers share a comparable kg DM per kg LW metric instead of raw head per hectare.
Classroom and extension demos of residual and density
Show students how residual mass and area unit choice change available forage and forage allowance without rebuilding a spreadsheet each time.
FAQ
How do I calculate forage allowance?
Forage allowance is available forage kilograms divided by total live weight kilograms.
What units does the forage allowance calculator use?
Herbage and residual are kg dry matter per hectare. Live weight is kilograms per animal. The main result is kg forage DM per kg live weight.
How is forage allowance different from stocking rate?
Stocking rate is animals per unit area. Forage allowance divides available forage mass by total live weight, so heavier animals reduce allowance even at the same head count and paddock size.
Why subtract a residual mass before calculating forage allowance?
Because the residual is the forage you plan to leave for regrowth, soil cover or animal welfare. It comes off the herbage mass before the division, and the usable amount never drops below zero.
What does the result look like for 40 cows on 4 hectares?
With 2500 kg of dry matter per hectare, 800 kg left behind and cows of 450 kg, you get 6800 kg on offer for 18000 kg of live weight, or 170 kg per animal. The allowance is that forage divided by the live weight.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/bio/forage-allowance \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"herbage_mass":2500,"area":4,"animal_count":40,"live_weight":450}'const res = await fetch("https://api.kit.forhosting.com/bio/forage-allowance", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"herbage_mass": 2500,
"area": 4,
"animal_count": 40,
"live_weight": 450
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/bio/forage-allowance",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"herbage_mass": 2500,
"area": 4,
"animal_count": 40,
"live_weight": 450
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/bio/forage-allowance", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"herbage_mass":2500,"area":4,"animal_count":40,"live_weight":450}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"herbage_mass":2500,"area":4,"animal_count":40,"live_weight":450}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/bio/forage-allowance", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"herbage_mass": 2500,
"area": 4,
"animal_count": 40,
"live_weight": 450
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "bio.forage_allowance",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
The algorithm is pure deterministic arithmetic—no network and no model tokens—so the free browser path and the API agree on every finite input, and invalid values fail cleanly with invalid_input.
What forage allowance means and how it is calculated
The classical definition used here is available forage dry-matter mass divided by total animal live weight: FA equals available forage in kilograms divided by total live weight in kilograms, with units of kilograms of dry matter per kilogram of live weight.
Input contract, response fields, and validation errors
A formula string restates the identity used. Example: herbage mass two thousand five hundred kilograms of dry matter per hectare, residual eight hundred, four hectares, forty animals at four hundred fifty kilograms yields available density one thousand seven hundred kilograms per hectare, available forage six thousand eight hundred kilograms, total live weight eighteen thousand kilograms, and forage allowance of six thousand eight hundred over eighteen thousand. POST a JSON body with four required finite numbers: herbage_mass (non-negative kilograms of dry matter per hectare of standing or pre-graze forage), area (positive paddock area), animal_count (positive head count), and live_weight (positive mean kilograms per animal). residual_mass is optional and defaults to zero; when sent it must be a non-negative finite number in the same kilograms-per-hectare units. area_unit is optional and defaults to hectare; accepted values are hectare or acre with common aliases such as hectares, ha, acres, and ac. Parameter aliases from the schema work the same way: forage_mass, dm_mass, available_dm, paddock_area, animals, head, body_weight, lw, residual, and related names. Each numeric field may arrive as a JSON number or as a numeric string; empty strings, missing required keys, non-finite values, zero or negative area or stock or weight, and negative herbage or residual fail with invalid_input naming the problem and are not billed. On success the body echoes herbage_mass, residual_mass, available_density_kg_ha, area, area_unit, area_hectares, area_acres, animal_count, and live_weight. Mass and ratio fields include available_forage_kg, total_live_weight_kg, forage_allowance and forage_allowance_kg_per_kg (identical main ratio), forage_allowance_kg_per_100kg_lw, forage_per_animal_kg, stocking_rate_per_ha, and stocking_rate_per_acre. Boolean has_available_forage is true when available forage mass is strictly positive. Successful calls use prepaid KIT balance at the published $0.002 base price per item.
Where a forage allowance calculator earns its keep
Pair results with intake targets and graze duration if you later convert allowance into daily feed budgets—those steps are outside this endpoint, which focuses on the instantaneous mass-per-live-weight ratio. Keep herbage samples representative of the grazable horizon, weigh a fair sample of the herd when mean live weight is uncertain, and treat the API output as a planning aid you reconcile with fence lines, water points, and animal class on the ground.
Technical questions
What is residual_mass for?
Residual mass is the kg DM/ha you plan to leave after grazing. Available density is max(0, herbage_mass − residual_mass). Omit it or send 0 when the full standing crop is treated as available.
What does the forage allowance calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.