8-Minute Rule Calculator
Eight minutes is the magic number in therapy billing. Enter total timed minutes for the visit and get the billable units instantly — plus a splitter that assigns units across several timed codes the way Medicare does.
Therapy timed codes are not billed by the clock alone — they are billed by the 8-minute rule. Under Medicare's rule, a unit is earned only when a timed service reaches at least 8 minutes, and total timed minutes drive the total units for the visit. Enter the minutes and see the units, how far you are into the current unit, and how many more minutes would earn the next one.
Calculate billable units
Split the units across codes
When a visit mixes several timed codes, the total units come from the total timed minutes — not from rounding each code separately. List each timed code and its minutes, one per line:
The rule, as a table
- 0–7 minutes — 0 units
- 8–22 minutes — 1 unit
- 23–37 minutes — 2 units
- 38–52 minutes — 3 units
- 53–67 minutes — 4 units
- 68–82 minutes — 5 units (and so on: each further unit needs its span to reach the next 8-minute threshold)
In formula form: units = floor((total timed minutes + 7) / 15) once the total reaches 8 minutes, and 0 below that. This is the Medicare (CMS) method. Some commercial payers and Medicaid plans instead round each code separately (the so-called AMA method), which can produce a different unit count for the same visit — know which method each payer in your mix requires before the units go on the claim. Untimed codes (evaluations, supervised modalities such as unattended electrical stimulation) are billed separately and never enter the minute total. Therapy unit errors are a staple of PT and OT denials; our physical therapy billing team checks units against documented minutes on every claim.
Frequently asked questions
What is the 8-minute rule in simple terms?
A timed therapy unit is only billable once the service reaches 8 minutes. After that, each additional unit needs the total to cross the next threshold — 23 minutes for 2 units, 38 for 3, 53 for 4. Equivalently: units = floor((minutes + 7) / 15) for any total of 8 minutes or more.
Do I total the minutes or round each code separately?
Under the Medicare method, total first: the visit’s combined timed minutes set the total units, which are then assigned to the individual codes. Some commercial payers use a per-code rounding method instead, which can yield more units for the same visit — applying the wrong payer’s method is a common source of therapy denials and overpayment findings.
Do untimed codes count toward the minutes?
No. Untimed services — evaluations and re-evaluations, and supervised modalities that do not require the therapist’s direct attendance — are billed per service, not per unit of time, and their minutes never enter the 8-minute rule total.