Undeny8-minute rule calculator
Enter each timed code and its minutes. The calculator applies Medicare's 8‑minute rule and shows how many units to bill for each code.
Therapeutic exercise
Manual therapy
Enter only 15-minute timed codes. Untimed codes (evaluations such as 97161-97163, or 92521) are billed as 1 unit regardless of minutes.
40 timed minutes · 38–52 minutes = 3 units
Bill 3 units in total
97110
33 min · Therapeutic exercise
2 units
97140
7 min · Manual therapy
+1 unit for the most remaining minutes (7).
1 unit
Medicare rule (CMS Pub. 100-04, Ch. 5, §20.2). Each code first gets one unit per full 15 minutes; leftover units go to the codes with the most remaining minutes. Other payers may count units differently.
What is the 8-minute rule?
The 8-minute rule is how Medicare turns minutes of 15-minute timed therapy codes into billable units. CMS sets it out in the Medicare Claims Processing Manual, Chapter 5, section 20.2. A timed service performed alone needs at least 8 minutes to bill one unit. When several timed services happen on the same day, you add up all the timed minutes, and that total decides how many units you can bill in all.
Minutes to units
CMS publishes this table for total timed minutes in a day. The pattern continues past two hours.
| Units | Total timed minutes |
|---|---|
| 1 | 8 through 22 |
| 2 | 23 through 37 |
| 3 | 38 through 52 |
| 4 | 53 through 67 |
| 5 | 68 through 82 |
| 6 | 83 through 97 |
| 7 | 98 through 112 |
| 8 | 113 through 127 |
How units are split across codes
- Add the minutes of every 15-minute timed code for the day and read the total units from the table.
- Give each code one unit for every full 15 minutes it was performed. A service done for at least 15 minutes always gets at least one unit.
- Give any units still left to the codes with the most remaining minutes. If two codes tie, CMS lets you choose either.
- If units run out, a short service gets none. Document it in the treatment note, but don't bill it.
CMS's worked examples
These are the five examples in section 20.2. Load any of them in the calculator above with the example buttons.
- 24 minutes of 97112 and 23 minutes of 97110: 47 minutes, so 3 units. Bill 2 units of 97112 and 1 of 97110.
- 20 minutes each of 97112 and 97110: 40 minutes, so 3 units. Bill 2 units of either code and 1 of the other.
- 33 minutes of 97110 and 7 minutes of 97140: 40 minutes, so 3 units. Bill 2 units of 97110 and 1 of 97140, because 97140's 7 minutes beat 97110's 3 leftover minutes.
- 18 minutes of 97110, 13 of 97140, 10 of 97116 and 8 of 97035: 49 minutes, so 3 units. Bill 1 unit each of 97110, 97140 and 97116; the ultrasound gets none.
- 7 minutes each of 97112, 97110 and 97140: 21 minutes, so 1 unit. Bill one of the three codes.
When it doesn't apply
Untimed codes, such as therapy evaluations and re-evaluations, are billed as one unit no matter how long they take. The rule is Medicare's: commercial and Medicare Advantage plans set their own unit rules, so check the payer's policy. CMS also expects the total timed minutes to be documented in the record (Medicare Benefit Policy Manual, Chapter 15, section 220.3).
Sources
- CMS, Medicare Claims Processing Manual, Chapter 5, §20.2
- CMS, Medicare Benefit Policy Manual, Chapter 15, §220.3
Informational only, not billing advice. See also modifier KX and modifier GP.
Questions billers ask
Something else? Email hello@undeny.ai.
What is the 8-minute rule?
It is Medicare's method for converting minutes of 15-minute timed therapy codes into billable units. A single timed service needs at least 8 minutes for one unit, and when several timed services are performed on the same day, the total timed minutes decide how many units can be billed.
How many units is 38 minutes?
Three units. Under the CMS table, 38 through 52 total timed minutes equals 3 units. If those minutes are split across several codes, each code first gets one unit per full 15 minutes and any remaining unit goes to the code with the most leftover minutes.
Does the 8-minute rule apply to evaluations?
No. Untimed codes, such as physical therapy evaluations or a speech-language evaluation like 92521, are billed as one unit regardless of how long they take. Only 15-minute timed codes are counted under the 8-minute rule.
Do commercial insurers use the 8-minute rule?
Medicare requires it. Commercial and Medicare Advantage plans set their own unit-counting rules and may not follow the CMS method. Check the payer's billing policy before applying the Medicare method to a non-Medicare claim.
What if a code doesn't get a unit?
When total timed minutes are used up, a short service may not receive a billable unit. CMS says you still document it in the treatment note; you just don't bill a unit for it.
What happens if units are billed incorrectly?
Payers may deny or reduce the line, often with a frequency or units-related adjustment. If you billed correctly under the rule, the appeal generator can draft a letter citing the timed minutes in your documentation.
Help build the full product
The free generator is the first piece. Next, Undeny reads denials from your remits, drafts every appeal and tracks it to payment. The first 100 practices shape it.
- A free denial audit at launch that shows what's recoverable
- Founding pricing, locked in before public rates
- First access to the full product, limited to 100 practices
- A direct line to shape what we build first
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