Converting units to minutes and minutes to units
Both directions, plus the single minutes that are worth a whole unit.
To convert therapy units to minutes under the US Medicare Part B 8-minute rule, count 8 minutes for the first unit. Add 15 more for each unit after it. So 2 units need at least 23 timed minutes, 3 units need 38, and 4 units need 53.
The same table read the other way converts minutes to units.
Minutes to units: the 8 minute rule table
Under US Medicare Part B, the first unit needs 8 timed minutes and each unit after that needs another 15.
| Total timed minutes | Units |
|---|---|
| 0 to 7 | 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 |
As a formula, for 8 minutes or more: units = floor((minutes − 8) ÷ 15) + 1. Below 8 minutes the answer is zero. The pattern continues the same way above two hours: 128 minutes is 9 units.
Units to minutes
Read the other way, the table gives the least treatment time for each number of units. It also gives the most you can deliver before the next unit starts.
| Units | Minimum minutes | Maximum before next unit |
|---|---|---|
| 1 | 8 | 22 |
| 2 | 23 | 37 |
| 3 | 38 | 52 |
| 4 | 53 | 67 |
| 5 | 68 | 82 |
| 6 | 83 | 97 |
| 7 | 98 | 112 |
| 8 | 113 | 127 |
The formula: minimum minutes = 8 + (units − 1) × 15. For 5 units, that is 8 + 4 × 15 = 68 minutes.
The threshold minutes
Some single minutes are worth a whole unit. Going from 22 to 23 minutes, or from 37 to 38, adds a unit. Dropping from 23 to 22 removes one.
The thresholds are 8, 23, 38, 53, 68, 83, 98 and 113.
Close to one of these minutes, it is tempting to round up to reach the next unit, so this is where accurate recording matters most. Record the minutes delivered.
Convert per patient, per calendar day
Under US Medicare, the timed minutes are totaled for each patient on each calendar day, and the table is applied once to that total.
Minutes from different patients never combine. Six patients who each receive 22 timed minutes bill one unit each, so the day is six units. Adding their 132 minutes into one block would give 9 units, which is wrong.
Minutes for the same patient on the same day do combine, even across two sessions. A patient seen for 10 timed minutes in the morning and 10 in the afternoon has 20 timed minutes that day, which is one unit. Converting each session on its own would give two units, which is also wrong.
Several timed codes in one day
When a patient has more than one timed code in a day, total the minutes, convert once, then share the units. Each code first gets one unit for every full 15 minutes it has. Any units still left go to the codes with the most minutes left over.
Example: 20 minutes of therapeutic exercise and 18 of manual therapy total 38 minutes, which is 3 units. Therapeutic exercise takes one unit for its first 15 minutes and has 5 left over. Manual therapy takes one unit and has 3 left over. The third unit goes to therapeutic exercise, because 5 minutes left over is more than 3. Therapeutic exercise bills 2 units and manual therapy bills 1.
The 8-minute rule calculator does this for up to four timed codes and shows the units for each code. The 8-minute rule guide works through four examples, including a code with under 8 minutes that still earns a unit.
Units to credited minutes, if your employer counts that way
Some employers calculate productivity from billed units multiplied by 15 instead of actual minutes. Then the conversion runs a third way.
| Actual minutes | Units | Credited minutes (units × 15) | Difference |
|---|---|---|---|
| 22 | 1 | 15 | −7 |
| 23 | 2 | 30 | +7 |
| 30 | 2 | 30 | 0 |
| 37 | 2 | 30 | −7 |
| 38 | 3 | 45 | +7 |
| 45 | 3 | 45 | 0 |
| 52 | 3 | 45 | −7 |
Example: a day of fourteen 22-minute treatments, each with a different patient. Each treatment loses 7 credited minutes, so the day loses 14 × 7 = 98 credited minutes. On a 450-minute paid day (8 hours with a 30-minute unpaid lunch, as an example), 98 minutes is 21.8 percentage points of productivity. Fourteen 23-minute treatments gain the same 98 minutes.
Treatment length is a clinical decision, and the credit gap doesn't change that. It is still worth knowing how your employer counts, so you can read your own figure.
A quick self-check
Two checks catch most errors before they reach a claim. A patient's total units for the day should never be more than the day's total timed minutes divided by 15, rounded up. And a day with under 8 timed minutes in total bills no timed units, however much untimed service was delivered alongside them.
If either check fails, the minutes were probably entered against the wrong code, or an untimed service got into the timed total. A single code with under 8 minutes is not an error on its own. Its minutes count toward the day's total, and it can still earn a unit.
When a payer counts each code separately
Some commercial payers count each code separately, an AMA CPT time convention, instead of totaling first. The same visit can then bill a different number of units. Check each payer's policy before you apply this table to its claims. Payers outside the US set their own rules, and the Medicare table doesn't apply to them.
Keeping the table to hand
The first unit needs 8 minutes and every unit after it needs 15, so you can rebuild any row from those two numbers. For a quick prompt, write 8, 23, 38 and 53 on a card. Those four thresholds cover visits up to an hour, which is enough to check what your billing system suggests before you sign the note.
This guide is general information about the US Medicare rule. It is not billing, coding or legal advice. Your billing department, your payer's rules and current CMS guidance decide any claim.