How to Map Your Pastures for Free (Acres, Paddocks & Grazing Records)

Field Forge 3D · Field guide

Most grazing questions start with the same three numbers: how many acres is each pasture, what's grazing there right now, and when did it go in? Plenty of operations run those numbers from memory, a whiteboard in the barn, or a guess made from the road. The tools to do better are free — here's how to get real acres on every pasture, sketch paddock splits over the actual terrain, and keep grazing records that don't live in your head.

Why pasture acres are the number under everything

Acres are the input to nearly every grazing decision: pasture rent is priced per acre, seed and fertilizer go out per acre, and every stocking-rate rule of thumb — however you compute it — starts with how many acres you're actually turning stock onto. A pasture you've always called "the eighty" that measures 63 usable acres changes the math on all of it.

One honest framing up front: an acre measured off any map is a map measurement, not a legal survey. It's the same standard map acre that leases, FSA paperwork, and landlords work from — good enough to run a grazing plan on, not a substitute for a surveyor when a boundary itself is in question (here's the field guide on property lines).

Free ways to get acres on every pasture

• FSA maps. If the ground is enrolled, your local Farm Service Agency office can print tract maps with measured acres — the figures most rental agreements already reference.
• The county GIS parcel viewer. Good for whole-parcel acres and orientation, but parcel lines are tax maps, not fence lines — and they won't split a parcel into the pastures you actually rotate through.
• Google Earth. The polygon tool measures any shape you trace. It works, but each measurement is a one-off — there's no tidy place for the per-pasture records that make the acres useful.
• Draw them once, keep them. A purpose-built mapper lets you trace each pasture off the fence lines you can see in aerial imagery, get the acreage instantly, and keep the boundary — with its records — instead of re-measuring every time.

Paddocks: sketch the splits before you buy the wire

If you're subdividing for rotational grazing, sketching the splits on a map first is cheaper than moving posts twice. Drawing candidate paddocks over aerial imagery answers the layout questions early: are the paddocks actually close to equal acres, does each one reach water and shade, and does the lane land where the gates make sense?

Terrain belongs in that conversation too. A paddock that looks square from above can be half steep ground stock won't use evenly — seeing the pasture on real 3D terrain shows the slopes, draws, and low corners a flat map hides. (If standing water is part of the problem, there's a separate field guide on mapping drainage.) The map is for planning, though — walk the line before you drive the first post.

Grazing records worth keeping

The record that makes rotation work is boring on purpose: which pasture, what stock, how many head, in when, out when — plus what you noticed (forage condition, water, fence). Kept per pasture over a season or two, it answers the questions memory fudges: how long each pasture actually rested, which ones carry more than their acres suggest, and which one always goes backward in August.

A spreadsheet can hold all that, but spreadsheets drift — one tab per year, columns that change meaning, and none of it attached to the map you plan on. Keeping the records on the pasture boundary itself is what makes them usable at a glance.

One free map for the acres and the records

Field Forge 3D's Ranch Mapper is a free web app built to be that one map. It isn't produce-only: pick the grazing setup and the app relabels around how a stock operation talks — ranch and pastures — with units like head and AUM ready in an editable library, alongside whatever units you add yourself.

• Draw each pasture over real aerial imagery on 3D terrain, or import boundaries you already have (KML, KMZ, zipped Shapefile, GeoJSON — the import field guide).
• Acres on every pasture — the standard map acre, measured from the boundary as drawn or imported.
• Per-pasture records — dated entries in your own units (head, AUM, bales, or anything you define), with notes, kept right on the pasture — and exportable to CSV while in beta.
• Works offline in the truck, where pasture decisions actually get made. Free while in beta — nothing locked today, no sign-up needed to start.

What the map can't tell you

• Carrying capacity. Acres are the input, not the answer. Stocking rates depend on forage production, rainfall, and range condition — your county extension office or NRCS can put local numbers behind an AUM. No honest map tool computes that from a boundary.
• What actually happened. The grazing record is a record you keep, not a sensor — it's only as current as your last entry. There's no collar tracking or automatic rotation schedule here.
• Where the fence legally goes. Pasture boundaries traced from imagery follow the fences you can see, which aren't always the property line. Boundary questions are surveyor territory.

The short version

Get real acres on every pasture once, from FSA maps or a boundary you trace yourself. Sketch paddock splits over real terrain before you buy wire. Keep the boring in/out record per pasture instead of per memory. And keep all of it on one map you can open in the truck — the acres, the splits, and the season's grazing history in the same place.