Select your codes and enter minutes to calculate billable units.
This is the conversion table every therapy biller works from. Total the minutes of all timed services in the visit, find the band, and read across for the number of units you may bill.
| Total timed treatment minutes | Billable 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 |
| 83 – 97 minutes | 6 units |
| 98 – 112 minutes | 7 units |
| 113 – 127 minutes | 8 units |
Each band is 15 minutes wide, and each one begins 8 minutes into the next 15 minute block. That is the whole logic of the rule: 15 minutes is the nominal unit, and 8 minutes is the majority of it, so once you pass the halfway point of a block you have earned the unit. Below 8 minutes you have not, and the service cannot be billed on its own.
You do not need the chart if you remember the arithmetic. Divide the total timed minutes by 15 to get the whole units. Then look at the remainder: if the remainder is 8 or more, add one more unit; if it is 7 or fewer, drop it. Fifty-two minutes is 3 remainder 7, so 3 units. Fifty-three minutes is 3 remainder 8, so 4 units. One minute of documentation is the difference between three units and four.
The critical instruction is what you total. Under Medicare you total all timed minutes across all timed codes in the session before applying the rule once. You do not calculate each code separately and add the results up — that is a different method, produces a different answer, and is the single most common way therapy claims get overbilled.
These two methods share a threshold and almost nothing else, and mixing them up costs practices money in both directions. Take a visit with 20 minutes of therapeutic exercise (97110) and 10 minutes of manual therapy (97140).
| Method | How it counts | Result |
|---|---|---|
| Medicare 8 minute rule | Pools 20 + 10 = 30 total timed minutes, applies the rule once | 2 units |
| AMA Rule of Eights | 97110 at 20 minutes is 1 unit; 97140 at 10 minutes is 1 unit | 2 units |
Here they agree. Now change it to 20 minutes of 97110 and 7 minutes of 97140. Medicare pools 27 minutes and pays 2 units. The AMA method looks at 97140 alone, sees 7 minutes, and pays nothing for it — 1 unit total. The reverse also happens: three services of 8 minutes each give 24 pooled minutes and 2 Medicare units, but 3 units under the AMA method because each one independently clears the threshold. The payer decides which method applies, not the provider. Check the contract before you assume, and never apply one payer's method across the whole schedule.
The rule applies only to time-based CPT codes. Service-based (untimed) codes are billed once per session no matter how long they take, and their minutes must never enter the timed total.
| Timed codes (subject to the rule) | Untimed codes (1 unit per session) |
|---|---|
| 97110 — Therapeutic exercise | 97010 — Hot / cold packs |
| 97112 — Neuromuscular re-education | 97012 — Mechanical traction |
| 97116 — Gait training | 97014 — Electrical stimulation (unattended) |
| 97140 — Manual therapy | 97016 — Vasopneumatic devices |
| 97530 — Therapeutic activities | 97018 — Paraffin bath |
| 97535 — Self-care / home management | 97022 — Whirlpool |
Note that Medicare bundles 97010 entirely — it is never separately payable, even though it is a valid code. Billing it as a standalone line is a reliable way to generate a denial for a service you genuinely provided.
A Medicare patient receives 22 minutes of therapeutic exercise (97110), 13 minutes of manual therapy (97140), and 10 minutes of hot packs (97010) in a single visit.
First, remove the untimed code: 97010 is bundled and contributes zero minutes to the calculation. That leaves 22 + 13 = 35 timed minutes. Thirty-five divided by 15 is 2 remainder 5. Five is below 8, so it drops. The visit bills 2 units.
Now allocate them. CMS instructs you to bill the units for the service with the greatest time, so 97110 at 22 minutes takes the first unit and, having more time than 97140, takes the second as well — or you may bill 1 unit of each, which many practices prefer because it reflects the treatment delivered. What you may not do is bill 2 units of 97110 and 1 unit of 97140, because the pooled total only supports two units in the visit.
If you bill therapy services, these are the related tools and references most practices use alongside this one: the timely filing calculator for submission and appeal deadlines, the E/M code level calculator for evaluation visits, the global period calculator when therapy follows surgery, and the Medicare therapy threshold & KX calculator for the annual limit, the physical therapy billing service page. For denial handling, the denial code lookup covers the codes therapy claims hit most often, and our full 8 minute rule guide goes deeper on documentation.
Correct unit calculation, clean documentation and payer-specific method handling — we bill physical, occupational and speech therapy practices across the United States.
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