Net Mineral Acres vs Net Royalty Acres vs Decimal Interest

Three different measurements get used to describe mineral ownership, and they are routinely mixed up, sometimes carelessly and occasionally on purpose. If a buyer quotes you a price per acre, the first question to ask is which kind of acre they mean, because the answer can change the value of the offer by half.

The three measurements

Your decimal interest is a fourth number, and it is different again: it is your share of one specific well, which depends on the size of the drilling unit. That is covered separately in how to calculate your royalty decimal interest.

Net mineral acres: what you own

Net mineral acres are the plainest measure. If you own all the minerals under a 160-acre tract, you own 160 net mineral acres. If you inherited a quarter of that, you own 40. It says nothing about your lease or your royalty rate, only about the size of your ownership.

This is the number that appears in deeds and probate records, and it is the one most owners can work out from their documents. It is also the number that does not change when you sign a new lease.

Net royalty acres: what the income is worth

Here is the problem net royalty acres exist to solve. Two owners each hold 40 net mineral acres in the same unit. One is leased at one-eighth, the other at one-quarter. The second owner receives twice the income from identical acreage. Quoting both as 40 acres makes them look equivalent when they are not.

So the industry standardizes to the historical one-eighth royalty. Multiply your net mineral acres by your royalty rate divided by one-eighth, and you get net royalty acres, a figure that can be compared across leases.

Note what this means for an unleased interest. With no lease, there is no royalty rate, so there are no net royalty acres to quote. Unleased minerals are valued as net mineral acres, on the expectation of a future lease.

Why this matters when an offer arrives

Suppose you own 40 net mineral acres leased at three-sixteenths, which is 60 net royalty acres. A buyer offers 12,000 dollars per acre. Which acre?

Most reputable buyers are clear about this without being asked, and quoting in net royalty acres is standard practice rather than a trick. The danger is not usually deception. It is comparing two offers quoted on different bases and concluding the wrong one is better. Our guide on responding to offer letters covers the questions worth asking.

A quick way to keep them straight

• Gross acres: the size of the tract.
• Net mineral acres: how much of it you own.
• Net royalty acres: how much income that ownership actually produces, standardized to one-eighth.
• Decimal interest: your share of one particular well, after the drilling unit is taken into account.

If you are working from old documents and cannot pin down your net mineral acres, that is normal, and it is usually resolvable from deeds and county records. Our guide on first steps after inheriting mineral rights walks through the paperwork, and state pages for Texas, New Mexico, and North Dakota cover local specifics.

Once you know what you own, finding out what it is worth is straightforward. You can request a free valuation at any time, with no obligation and no pressure to sell.