Montana Mineral Royalty Calculator: Your Decimal Interest

Step 1: Gather your three inputs

Your net mineral acres in the tract, the unit's spacing acres, and your lease royalty rate — from your deed, your lease, and the Board of Oil and Gas unit record.

Step 2: Compute your decimal

Decimal interest = net mineral acres ÷ unit acres × royalty rate. Use the royalty calculator to check your math.

Step 3: Account for what Montana takes out

A variable oil & gas production tax (a low rate during the drilling-incentive window, higher afterward) is withheld, so your net check is below the gross your decimal implies — plus any post-production deductions your lease allows.

Step 4: Verify against your Montana division order

The decimal on the division order must match your calculation. If it is low, the operator may have the wrong net acres, unit size, or royalty rate — reconcile it before you sign.

Step 5: Get it audited

Have the decimal and the check history verified. Valor audits Montana royalties stub by stub as an independent mineral manager.

What is Montana-specific about your royalty math

The decimal-interest formula does not change by state, but Montana facts change what you actually receive. Tax: Montana levies a variable oil & gas production tax (a low rate during the drilling-incentive window, higher afterward), withheld before or alongside your royalty, so your net is below the gross your decimal implies. Timing: Montana law generally requires operators to begin paying proceeds once title is marketable in the owner's name, and to pay on a regular cycle thereafter, and like most producing states, Montana can impose statutory interest on royalty proceeds held past the period the law allows — confirm the current Montana rate. Unit size: the acres you divide by depend on how Montana forms drilling units — Montana allows compulsory pooling under Title 82, ch. 11, so an unleased owner can be pooled into a unit — which decides whether your tract stands alone or sits inside a larger pooled unit (a bigger denominator, and a smaller decimal on more total production). Verification: spacing and production are regulated by the Montana Board of Oil and Gas Conservation, whose records confirm the unit acres in your decimal, and your Montana division order should state a decimal that matches net mineral acres ÷ unit acres × royalty rate. If your Montana division-order decimal does not match your own calculation, do not sign until it is reconciled; an incorrect decimal underpays you every month it goes uncorrected.

Montana facts at a glance

The Montana-specific facts that shape this situation — a citable reference. General guidance as of September 2026; confirm specifics with a CPA or attorney.