8-Minute Rule Calculator for Physical Therapy Billing
By ePT Billing. Updated 1 October 2026. Medicare math checked against all five worked examples in CMS's manual.
Quick answer: Under Medicare's 8-minute rule, add up all timed minutes for the day, then convert the total to units: 8 to 22 minutes is 1 unit, 23 to 37 is 2, 38 to 52 is 3, and so on. Give each code its full 15-minute blocks, then place any leftover units on the codes with the most leftover minutes. (Source: CMS manual, Ch. 5, sec. 20.2 C)
ePT Billing works only with physical therapy professionals. It has over 200 clients, and every claim is audited before it goes to the payer. This is the unit math behind every Medicare PT claim with timed codes.
The free 8-minute rule calculator below does the math for you. Type the minutes for each code and it shows Medicare units and CPT midpoint units side by side, with the working written out. Nobody went to PT school to do remainder math at 6 pm.
On this page: Calculator | Minutes-to-units chart | CMS examples | Medicare vs CPT | Mistakes | FAQ
Free 8-minute rule calculator
Enter the minutes for each timed code from one date of service, and tick any untimed codes. The left column follows Medicare's method. The right column follows the CPT midpoint method that some commercial payers use. Want proof it works? Load any of the five CMS examples and compare the answer with the manual.
8-Minute Rule Calculator
Type the minutes for each timed code. Results update as you type: Medicare's 8-minute rule on the left, the CPT midpoint rule on the right.
Medicare: CMS 8-minute rule
Original Medicare, and any payer that follows the CMS method
0 timed units
Enter minutes to see the math.
CPT midpoint rule ("rule of 8s")
Some commercial payers. Check your contract and payer policy.
0 timed units
Enter minutes to see the math.
Document in the note: total timed minutes 0, total treatment time 0 minutes.
Educational tool only, not billing or legal advice. Payer policies and contracts vary, so check the payer's own rules before you bill. Medicare math follows the Medicare Claims Processing Manual, Chapter 5, section 20.2 and is tested against all five of its worked examples, plus the unit counts and tie-breaker in CMS's CQ/CO billing examples. Code names are plain-English labels, not official CPT descriptors. CPT is a registered trademark of the American Medical Association. Calculator by ePT Billing.
How many units is my time? The 8-minute rule chart
Medicare turns total timed minutes into units with a fixed chart. 8 to 22 minutes is 1 unit, 23 to 37 is 2, 38 to 52 is 3, and each extra 15 minutes adds 1 more. Under 8 total timed minutes, you bill no timed units at all.
| Total timed minutes in the day | Timed units you can bill |
|---|---|
| Under 8 | 0 |
| 8 to 22 | 1 |
| 23 to 37 | 2 |
| 38 to 52 | 3 |
| 53 to 67 | 4 |
| 68 to 82 | 5 |
| 83 to 97 | 6 |
| 98 to 112 | 7 |
| 113 to 127 | 8 |
| 128 and up | 1 more unit per extra 15 minutes |
Every minute of direct treatment counts toward the total. CMS says the chart is only there to round time into 15-minute units. It does not mean the first 7 minutes get thrown out. (Ch. 5, sec. 20.2 C, note after Example 5)
How does the 8-minute rule work with more than one code?
Add every timed minute from the day, read the total units off the chart, then split those units between codes. Each code first gets one unit per full 15 minutes. Any units left over go to the codes with the most minutes left over. The total never goes above what the chart allows.
- Add up the timed minutes. Only codes billed in 15-minute units count. Evaluations and other untimed codes stay out of this number.
- Find the total on the chart. That is the most timed units you can bill for the day.
- Give each code its full 15-minute blocks. CMS says a service done for at least 15 minutes gets at least 1 unit, at least 30 minutes gets at least 2, and so on.
- Place the leftover units. Compare the minutes left over on each code and bill the larger. CMS walks through exactly this in its Example 3, below.
- Break ties. If two codes have the same minutes, or the same minutes left over, the tied unit can go to either code, but not both (CMS Examples 2 and 5, and the tie-breaker in CMS's CQ/CO guidance). Never pile every unit onto one code when another code got 15 minutes or more.
That is the method the Medicare column of the calculator uses, and it reproduces all five worked examples in section 20.2 of the CMS manual.
8-minute rule examples, straight from CMS
These three come from the Medicare Claims Processing Manual, Chapter 5, section 20.2 C. We added the CPT midpoint answer next to each one so you can see where the two methods split.
Example 1: 24 + 23 minutes = 3 units, not 4
| Code | Service | Minutes | Medicare units | CPT midpoint units |
|---|---|---|---|---|
| 97112 | Neuromuscular re-education | 24 | 2 | 2 |
| 97110 | Therapeutic exercise | 23 | 1 | 2 |
| Total | 47 | 3 | 4 |
47 minutes sits in the 38 to 52 band, so Medicare allows 3 units. Each code ran past 15 minutes, so each gets 1. The third unit goes to 97112 because it took more time. Count each code on its own, the CPT way, and you get 4 units: one more than Medicare allows.
Example 3: a 7-minute code still gets billed
| Code | Service | Minutes | Medicare units | CPT midpoint units |
|---|---|---|---|---|
| 97110 | Therapeutic exercise | 33 | 2 | 2 |
| 97140 | Manual therapy | 7 | 1 | 0 |
| Total | 40 | 3 | 2 |
40 minutes is 3 units. 97110 gets 2 units for its first 30 minutes, with 3 minutes left over. 97140 has 7 minutes. Compare the leftovers: 7 beats 3, so the third unit goes to 97140. Under the CPT midpoint method, 97140 never reaches 8 minutes on its own, so it is not billed and the day drops to 2 units.
Example 4: four codes, 49 minutes, only 3 units
| Code | Service | Minutes | Medicare units | CPT midpoint units |
|---|---|---|---|---|
| 97110 | Therapeutic exercise | 18 | 1 | 1 |
| 97140 | Manual therapy | 13 | 1 | 1 |
| 97116 | Gait training | 10 | 1 | 1 |
| 97035 | Ultrasound | 8 | 0 | 1 |
| Total | 49 | 3 | 4 |
49 minutes is 3 units, no matter how many services you did. The 3 units go to the three codes with the most time. The 8 minutes of ultrasound are not billed, but CMS says to still document them in the treatment note. Billing all four would be a Medicare over-bill: 4 units needs at least 53 minutes.
"...you may not bill 4 units for less than 53 minutes regardless of how many services were performed."
CMS, Medicare Claims Processing Manual, Chapter 5, section 20.2, Example 4
What about ties? CMS Example 2 has 20 minutes each of two codes, 40 in total. That bills 3 units: 2 on either code and 1 on the other, never 3 on one. CMS Example 5 has 7 minutes each of three codes, 21 in total, which bills 1 unit on any one of the three. The same applies when two codes tie on left-over minutes after their full 15-minute blocks and only one unit is left: the tie-breaker in CMS's CQ/CO billing guidance, which points back to these manual examples, says either may be billed, but not both. Load any of these into the calculator to see it. More quick fixes live in our 50 physical therapy billing tips.
What's the difference between the 8-minute rule and the CPT rule of 8s?
Medicare adds all timed minutes together, then caps units by the total. The CPT midpoint rule, which billers often call the rule of 8s, counts each code on its own: 8 minutes of a code earns a unit, 23 earns two. The same visit can bill more units or fewer, depending on the minutes.
| Medicare 8-minute rule | CPT midpoint rule ("rule of 8s") | |
|---|---|---|
| How minutes count | All timed minutes for the day, added together | Each code counted on its own |
| First unit | 8 total timed minutes | 8 minutes of that one code, counting whole minutes (APTA: the midpoint of 15 is passed at 7 minutes 31 seconds) |
| Each extra unit | Every 15 total minutes after that (23, 38, 53...) | Every 15 minutes of that code after that (23, 38, 53...) |
| A code under 8 minutes | Can still get a unit if it has the most minutes left over | Never billed |
| Can units outrun total time? | No. Total minutes cap the units | Yes. Four codes at 8 minutes each = 4 units from 32 minutes |
| Who uses it | Original Medicare | Payers whose policy follows CPT. Check each payer |
| Where the rule lives | CMS Claims Processing Manual, Ch. 5, sec. 20.2 | "Time" guidelines in the AMA's CPT codebook |
Which payers use which? There is no master list. APTA's guidance is to check each payer's policy, and if your contract says something different, the contract wins. APTA also recommends writing one coding approach into your clinic's policy manual. If a payer's manual is silent, a sensible habit (our suggestion, not a written rule) is to ask your rep in writing and keep the answer. Two rules, almost the same name, different math. Billing was never going to make this easy.
Do evaluation and untimed code minutes count toward the 8-minute rule?
No. Untimed codes, like PT evaluations and supervised modalities, bill 1 unit no matter how long they take, and their minutes stay out of the timed total. You still record them: Medicare wants both total timed minutes and total treatment time, which includes untimed minutes, in every treatment note.
| Code | Plain-English name | Timed or untimed | Medicare note |
|---|---|---|---|
| 97110 | Therapeutic exercise | Timed, 15-minute units | |
| 97112 | Neuromuscular re-education | Timed, 15-minute units | |
| 97116 | Gait training | Timed, 15-minute units | |
| 97140 | Manual therapy | Timed, 15-minute units | |
| 97530 | Therapeutic activities | Timed, 15-minute units | |
| 97535 | Self-care management training | Timed, 15-minute units | |
| 97161, 97162, 97163 | PT evaluation: low, moderate, high complexity | Untimed, 1 unit | 1 unit max per patient, per provider, per discipline, per day |
| 97164 | PT re-evaluation | Untimed, 1 unit | 1 unit max per patient, per provider, per discipline, per day |
| 97012 | Mechanical traction | Untimed, 1 unit | |
| 97010 | Hot or cold packs | Untimed, 1 unit | Bundled: Medicare never pays it separately (status B, and disposition 3 on the CY 2026 therapy code list) |
| 97014 | Electrical stimulation | Untimed, 1 unit | Not valid for Medicare (status I: Medicare uses another code) |
| G0283 | Electrical stimulation, unattended, other than wound care | Untimed, 1 unit | A HCPCS code, not CPT. Its descriptor says unattended, as part of a therapy plan of care |
Evaluations list a time, but they are still 1 unit. CMS's plain-language descriptions of 97161, 97162 and 97163, in the manual's unit-limit chart, say "typically 20 minutes", "typically 30 minutes" and "typically 45 minutes". That is the typical length of the evaluation, not a count of 15-minute units. A 45-minute high-complexity evaluation is still 1 unit, and its minutes stay out of the timed total (Ch. 5, sec. 20.2 B and D).
One exception worth knowing: caregiver training codes 97550 and 97551 do not round. For dates of service from 1 January 2025, CMS says the first 30 minutes (97550) and each extra 15 minutes (97551) can only be billed when the full time is provided. The calculator leaves these codes out of its unit math for that reason. Source: CMS annual therapy update, CY 2026 code list and dispositions.
8-minute rule mistakes to fix before an auditor finds them
Each of these breaks a written CMS rule, so each one is easy to spot from the note and the claim side by side. Unit errors are only one way claims come back. Here are 10 reasons physical therapy claims get denied.
- Billing every code on its own for Medicare. That is the CPT method. Medicare caps units by total timed minutes: in CMS Example 4, four services in 49 minutes bill 3 units, not 4. (Ch. 5, sec. 20.2)
- Piling all the units onto one code. If another code got 15 minutes or more, it gets at least 1 unit. CMS says not to count all of the day's minutes toward one code in that case. (Ch. 5, sec. 20.2 C, Examples 2 and 3)
- Counting time that isn't treatment. Setup before the patient is ready, rest breaks, toileting and waiting for equipment don't count. The clock starts when you are working directly with the patient. (Ch. 5, sec. 20.3)
- Double-counting two clinicians. If two people treat one patient at the same time, each 15 minutes of treatment still counts as one unit. CMS uses gait training in the parallel bars as its example. (Ch. 5, sec. 20.3)
- Leaving the totals out of the note. Every treatment note needs total timed code minutes and total treatment time, and the billing must be consistent with the timed minutes. (Pub. 100-02, Ch. 15, sec. 220.3 E)
- Not writing down timed services you didn't bill. Medicare wants every timed service recorded, billed or not, because unbilled minutes can change the units. (Ch. 15, sec. 220.3 E)
- Units that keep coming in short. CMS expects each unit to average 15 minutes of direct contact, and says a consistent habit of billing units under 15 minutes should be highlighted for review. (Ch. 5, sec. 20.2 C)
- Billing Medicare for codes it won't pay separately. Hot or cold packs (97010) are bundled, and 97014 is not valid for Medicare, which uses another code. (CMS RVU26D status codes) The HCPCS code described as unattended electrical stimulation as part of a therapy plan of care is G0283 (CMS HCPCS file, October 2026).
Using a PTA? Work out the units first, then decide which units carry the CQ modifier. CMS has a separate set of rules and worked examples for that step: CMS billing examples using CQ/CO modifiers. The calculator counts units only.
8-minute rule FAQ
Medicare answers below come from CMS Pub. 100-04, Ch. 5, sec. 20.2. CPT midpoint answers come from APTA's guide to timed codes.
What is the 8-minute rule in physical therapy?
It is Medicare's method for turning timed treatment minutes into billable 15-minute units. You add all timed minutes for the day, then use CMS's chart: 8 to 22 minutes is 1 unit, 23 to 37 is 2, and so on. Under 8 total minutes, no timed units are billed.
How many units is 38 minutes?
Under Medicare, 38 total timed minutes is 3 units, because 38 to 52 minutes is the 3-unit band. Under the CPT midpoint rule, it depends on how the 38 minutes split across codes, since each code is counted on its own.
Does the 8-minute rule apply to commercial insurance?
Only if the payer says so. Some commercial payers follow Medicare's method and some follow the CPT midpoint rule, which counts each code separately. APTA advises checking each payer's policy, and your contract overrides both.
Can you bill a code that took less than 8 minutes?
Under Medicare, yes, if the total timed minutes allow another unit and that code has the most minutes left over. In CMS's own Example 3, 7 minutes of manual therapy gets a unit. Under the CPT midpoint rule, no: a code needs 8 minutes on its own.
What if two codes have the same minutes?
CMS says to pick either one. In its Example 2, two codes at 20 minutes each bill 3 units: 2 on one code and 1 on the other. Never put all 3 units on one code.
Does the 8-minute rule apply to occupational therapy and speech-language pathology?
Yes, for timed codes. The rule sits in the Medicare manual chapter on outpatient rehabilitation, which covers physical therapy, occupational therapy and speech-language pathology, and CMS's own examples include occupational therapy codes.
Want someone else to check the units on every claim?
ePT Billing works only with physical therapy professionals. Every claim is audited before it goes out, denials are appealed the same day they are processed, and you can try us free for 30 days. See everything ePT Billing handles or book a call with Alex.
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Disclaimer: This calculator and page are educational. They are not billing, coding or legal advice. Medicare contractors and commercial payers publish their own policies, and contracts can override general rules, so check the payer's current policy before you bill. CPT is a registered trademark of the American Medical Association. Code names on this page are plain-English labels, not official CPT descriptors.
Sources
- CMS, Medicare Claims Processing Manual, Pub. 100-04, Chapter 5, sections 20.2 and 20.3
- CMS, Medicare Benefit Policy Manual, Pub. 100-02, Chapter 15, section 220.3
- CMS, Billing Examples Using CQ/CO Modifiers for Services Furnished by PTAs and OTAs
- CMS, 11 Part B Billing Scenarios for PTs and OTs
- CMS, Annual Therapy Update: CY 2026 therapy code list and dispositions
- CMS, Physician Fee Schedule Relative Value File RVU26D
- CMS, HCPCS quarterly update, October 2026
- APTA, Coding for Timed Codes
- Premera Blue Cross, Billing for Time (7 November 2019)