Illinois 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 IDNR 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 Illinois takes out

No general oil-and-gas severance tax (a graduated tax applies only to high-volume hydraulically fractured wells under the 2013 Illinois Hydraulic Fracturing Regulatory Act) 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 Illinois 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 Illinois royalties stub by stub as an independent mineral manager.

What is Illinois-specific about your royalty math

The decimal-interest formula does not change by state, but Illinois facts change what you actually receive. Tax: Illinois levies no general oil-and-gas severance tax (a graduated tax applies only to high-volume hydraulically fractured wells under the 2013 Illinois Hydraulic Fracturing Regulatory Act), withheld before or alongside your royalty, so your net is below the gross your decimal implies. Timing: Illinois 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, Illinois can impose statutory interest on royalty proceeds held past the period the law allows — confirm the current Illinois rate. Unit size: the acres you divide by depend on how Illinois forms drilling units — Illinois provides for compulsory integration (forced pooling) of drilling units under the Illinois Oil and Gas Act, 225 ILCS 725/22.2, administered by the IDNR, so an unleased Illinois owner can be integrated 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 Illinois DNR Office of Oil and Gas Resource Management, whose records confirm the unit acres in your decimal, and your Illinois division order should state a decimal that matches net mineral acres ÷ unit acres × royalty rate. If your Illinois 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.

Illinois facts at a glance

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