What NMA is
NMA means net mineral acres (also written net mineral acreage). It is not the surface tract and it is not the acres printed on the tax card. It is the mineral acres you actually own in a described tract after your undivided fraction is applied. Lease Bonus is almost always quoted per NMA. Pooling / unit royalty share is almost always NMA in the unit, not 100% of the well.
Cover sheets skip the arithmetic. A fat per-acre line on thin NMA is how a “great offer” is a small check — and how a mineral deed offer dressed as dollars per acre still sells whatever you own. This page is not legal advice. Mineral Vertex buys oil and gas minerals and matches owners with buyers. We do not promise to beat every letter.
Copies of the deed, any lease, a division order or stub, and the letter’s acreage line are enough to start. Do not notarize their form because the NMA “looks close.” Their worksheet is not a title opinion.
The formula
The working formula mineral buyers and landmen use:
NMA = gross mineral acres × undivided mineral interest
Gross mineral acres are the acres in the mineral legal — the survey, abstract, or section-township-range that describes the mineral estate, not always the surface farm. Undivided mineral interest is your fraction of 8/8 in that mineral estate (or in that depth, if the minerals were severed by horizon). Multiply. That product is NMA.
| Piece | What it is |
|---|---|
| Gross mineral acres | Acres in the mineral legal for the tract (or the depth slice you own). |
| Mineral interest | Your undivided fraction of 8/8 — 1/2, 1/4, 1/8, 3/16, whatever the deed chain says. |
| NMA | Gross acres × mineral interest. |
| Unit share | Your NMA ÷ unit acres (after Pooling / unit). |
| Approx. royalty decimal | Unit share × lease Royalty, then other burdens. |
If you own only a depth, the gross acres are still the tract acres for that slice, times your fraction in that slice. If four heirs own equally, each heir’s NMA is the parent NMA divided by four — unless a will or deed says otherwise. Proportionate reduction still shrinks bonus and royalty if the lease caption assumed 8/8 and you do not own 8/8.
Worked examples
| Facts | NMA |
|---|---|
| 160-acre mineral tract, you own 1/4 of the minerals | 160 × 1/4 = 40 NMA |
| Same 40 NMA, four equal heirs | 40 ÷ 4 = 10 NMA each |
| 80-acre tract, you own 1/2, minerals only below 8,000 feet | 80 × 1/2 = 40 NMA in that depth (zero above, unless a deed says otherwise) |
| You own 8/8 of 12.5 acres in a 640-acre unit | 12.5 NMA; unit share 12.5 ÷ 640 |
Those examples are arithmetic, not a title opinion. A reservation, a royalty deed, an old lease still HBP, or a depth severance can change the fraction before you ever multiply. Match the legal on the oil and gas map, then send the paper.
Bonus and royalty from NMA
Bonus is typically dollars × NMA, often after title, often after proportionate reduction. $2,500 per NMA on 40 NMA is $100,000 if they actually pay on 40. If their exhibit says 22 NMA, the check follows 22 until someone corrects the acres.
Inside a unit, your share of production is not “my royalty times the well.” The usual first cut is:
Royalty share ≈ (NMA ÷ unit acres) × lease royalty
Example: 40 NMA in a 640-acre unit, 1/5 royalty → (40 ÷ 640) × 0.20 = 0.0125 of 8/8 production — before overrides, NPRI, and post-production deductions. Read Royalty for types. A shut-in does not change your NMA; it can change whether the lease is held. See Shut-ins.
What NMA is not
- Surface acres — you can own 160 surface acres and 10 NMA, or 0 surface and 80 NMA.
- NRI (net revenue interest) — that is a pay-deck decimal after royalty and burdens, not acres.
- NPRI “royalty acres” — a Royalty deed / NPRI is a slice of the royalty stream, not the same product as NMA in the mineral estate.
- The letter’s NMA — underwriting, not chain of title. Heirs, reservations, and already-leased depths are how their number and yours diverge.
The letter’s NMA
Buyers pull tax rolls, old division orders, and last-known decimals, then print an NMA. That figure is what they will pay on until title says otherwise — and some packets never come back after title. Inherited minerals are the usual gap: one envelope, four heirs, one NMA line that assumes the addressee can convey all of it. See sell inherited minerals and what to do when you inherit mineral rights.
If the same envelope is a mineral deed, they are buying that NMA (or whatever the granting clause actually takes), not leasing it. Treat the lease and the deed as two deals. Location still changes the number. Match the county on locations.
What to read twice
- Whose acres — their exhibit vs your deed vs a stub.
- The fraction — 8/8 caption on a 1/4 owner is how proportionate reduction hits bonus.
- Depths — NMA in a shallow reservation is not NMA in the pay they are drilling.
- Heirs — one NMA line does not mean one person can sign.
- Unit math — NMA ÷ unit acres before you celebrate a royalty fraction.
- The legal — match survey or section-township-range on the oil and gas map.
Use how to respond if you need a week, then send NMA here — meaning the letter, the deed or lease, and any stub — so we can try an offer, a buyer match, or a counter.
Let us counter or match this offer
Photos or PDFs of the letter and every deed or lease page, the county, and whether you get royalty now. We buy minerals and we match owners with buyers. We will try a counter on their number, or put you with a buyer who might. We do not promise to beat every letter — we do ask you to send it before you sign.