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The 8 Minute Rule Calculator for Physical Therapy Units

The '8 minute rule' has become a crucial aspect of therapy services, especially when billing Medicare. This principle, while seemingly simple, can often become complex when applied to different scenarios. The 8 minute rule calculator will calculate physical therapy units and charges based on the services performed. Access the calculator below and calculate billable units quickly.

8 Minute Rule Calculator Thumbnail

How to Use the 8 Minute Rule Calculator

The 8 minute rule calculator will automatically calculate the units required to properly bill for physical therapy services.

Step 1: AMA or CMS?

Select the proper calculation method based on which insurance provider will be billed. Not sure if the insurance company uses the CMS 8 min rule or AMA rule of 8s? Read below for more details on which insurances use the 8 minute rule.

Step 2: Select Charges

Select the applicable charges based on the services or treatments provided during the patient appointment.

Step 3: Add Time

Adjust the amount of time (in minutes) based on the total treatment time for each service.

Step 4: Billing Units

The proper units for each charge will be automatically calculated. Now submit that claim and get reimbursed!

What is the 8 Minute Rule?

The '8 minute rule' is a principle used by therapists to calculate the number of billable units for a particular date of service. The rule stipulates that a therapist must provide direct therapy for at least eight minutes to be eligible for reimbursement for one unit of a time-based treatment code. It is crucial to understand that this rule applies to 'timed' or 'constant attendance' CPT codes, which are billed in 15-minute increments.

Example #1: A total 54 minutes of various rehab therapy was performed. Medicare 8 minute rule would divide 54 by 15, and quantify that time as three whole units with nine remaining minutes. Because more than eight minutes remain, we can bill an additional unit.

8 minute rule calculator

Time-Based Units vs Service-Based Units

Before we delve deeper into the '8 minute rule', it is essential to distinguish between time-based and service-based CPT codes.

Service-Based Units:

These billing units, also known as 'untimed' codes, denote services provided to the patient that are independent of time. Examples of service-based CPT codes include physical therapy evaluation or re-evaluation, hot/cold packs, and unattended electrical stimulation. Therapists can bill these codes only once per session, regardless of the time taken to complete the service. Common untimed codes include:

  • Physical therapy evaluation CPT Code — 97161, 97162, or 97163

  • Patient re-evaluation CPT Code — 97164

  • Electrical stimulation (unattended) - 97014

  • Hot/cold packs - 97010

  • Group therapy - 97150

Time-Based Units

Conversely, time-based units, also known as 'constant attendance codes', are billed in 15-minute increments. These codes apply to services that require one-on-one, skilled therapy for the duration of the service. Examples of time-based therapy CPT codes include therapeutic exercise, manual therapy, and ultrasound. Common timed codes include:

  • Therapeutic exercise - 97110

  • Manual therapy - 97140

  • Neuromuscular re-education - 97112

  • Electrical stimulation (manual) - 97032

  • Ultrasound - 97035

  • Gait training - 97116

  • Physical performance test or measurement - 97750

Understanding the Calculation for Billing Units

The 8-minute rule entails particular calculations to determine the number of billable units accurately. To correctly apply the rule, the total minutes of skilled or one-on-one therapy provided are added, and this sum is divided by 15. If the result leaves at least 8 minutes before reaching another 15-minute increment, an extra unit can be billed. However, if there are less than 8 minutes remaining, an additional unit cannot be billed.

Example #2: If a physical therapist provides 30 minutes of therapeutic exercises and 15 minutes of manual therapy, totaling 45 minutes, they can bill Medicare for 3 units since the remainder of 45 minutes (when divided by 15) is zero.

The 8 Minute Rule Cheat Sheet: How to calculate billable units

When determining the number of units you can bill for a timed service, CMS requires a minimum of 8 minutes of direct treatment for each billable unit. Additionally, each unit occurs in 15-minute increments. To provide further clarity, let's break it down in the chart below:

Time Spent (minutes)

Number of Units













Mixed Remainders

In some situations, when you divide the total timed minutes by 15, the remaining minutes may consist of more than one billing code. This situation is referred to as a 'mixed remainder'. Medicare guidelines allow billers to 'borrow' and 'round-up' other services to create whole units if there are enough remainder minutes.

For instance, if a therapist performed 21 minutes of manual therapy and 17 minutes of gait training, there would be 2 remainder minutes of gait training and 6 remainder minutes of manual therapy left. In this case, since the total remainder is 8 minutes (combined), the therapist can bill for another unit.

Introduction to the AMA’s Rule of Eights

The American Medical Association (AMA) uses a slightly different system called the “Rule of Eights,” also known as the Midpoint Rule. The rule of 8s considers each individual unit and does not allow for the addition of the total session time for all time-based codes used. You cannot bill for a unit unless the one-on-one treatment lasted at least 8 minutes. This rule differs from the Medicare 8 minute rule, which allows the addition of services to reach a total of 15 minutes, to bill for a unit.

Whats the Difference Between the CMS 8-Minute Rule and AMA Rule of 8's?

While both rules are designed to standardize the billing of therapy services, they apply differently in practice. The CMS 8-Minute Rule allows for the addition of services to reach a total of 15 minutes and bill for a unit. On the contrary, the AMA Rule of Eights considers each individual unit and does not allow for the addition of the total session time for all time-based codes used.

Example#3: CMS 8-Minute Rule vs AMA Rule of 8's

97110 - Therapeutic Exercise: 15 Minutes

97112 - Neuromuscular Re-education: 8 Minutes

97140 - Manual Therapy: 8 Minutes

AMA Rule of 8s:

97110 - Therapeutic Exercise: 1 Unit

97112 - Neuromuscular Re-education: 1Unit

97140 - Manual Therapy: 1 Unit

CMS 8 Min Rule:

97110 - Therapeutic Exercise: 1 Unit

97112 - Neuromuscular Re-education: 1Unit

97140 - Manual Therapy: 0 Units

15 minutes of therapeutic exercise, 8 minutes of neuromuscular re-ed and 8 minutes of manual therapy for a total of 31 minutes. According to the chart above, the maximum total codes you can bill for 31 minutes is 2. For CMS 8 min rule, bill one unit of therapeutic exercise plus one unit of either neuromuscular re-ed or manual therapy.

Which Insurances Follow the 8 Minute Rule?

The 8-minute rule is a billing principle set by the Center for Medicare and Medicaid Services (CMS). However, it is also used by several other insurance companies, including Medicaid, TRICARE, and certain private insurers that follow Medicare guidelines. However, it is always advisable to review the rules for each insurance company carefully to avoid billing issues, denials, and delays.

8 Minute Rule Examples

Example #4

30 minutes of neuromuscular re-education , 15 minutes of manual therapy, 8 minutes of ultrasound, and 15 minutes of electrical stimulation unattended. 30 min + 15 min + 8 min = 53 direct timed minutes, which supports four billing units.

The 15 minutes of ESTIM supports one additional service-based billing unit for a total of five units for this date of service.

Example #5

A physical therapist provides 15 minutes of therapeutic exercise (97110), 8 minutes of therapeutic activities (97530), and 5 minutes of manual therapy (97140). 15 + 8 + 5 = 28 minutes. 28 Minutes is 1 unit with a remainder of 13 minutes.

Bill for 2 units total, 1 unit for CPT Code 97110 (therapeutic exercise), and 1 unit for CPT Code 97530 (therapeutic activities).

Example #6 A physical therapist provides 21 minutes of therapeutic exercise (97110) and 20 minutes of manual therapy (97140). Total Treatment time equals 41 minutes.

Referencing the cheat sheet above we know that 41 minutes allows for 3 units. Inspecting this further therapeutic exercise (97110) is 1 unit with a mixed remainder of 6 minutes and manual therapy (97140) is one unit with a mixed remainder of 5 minutes. This total mixed remainder of 11 minutes is greater than 8 minutes, which allows us to round up to an extra unit for a total of three pt billing units. Therapeutic exercise (97110) 2 units, manual therapy (97140) 1 unit.

Final Thoughts: Ensuring Compliance with the 8 Minute Rule

Understanding and correctly applying the PT 8 minute rule is crucial for operating a in network therapy practice. It helps ensure accurate billing, improves the revenue cycle, and prevents potential audit issues.

By understanding the differences between time-based and service-based CPT codes, learning how to calculate billable therapy units, and being aware of the specific rules of different insurance companies, therapists can navigate the complexities of billing with greater ease and confidence.

As a final tip, consider investing in a comprehensive practice management software solution that includes built-in 8-Minute Rule functionality. This feature can automatically check your billing calculations, alert you to any inconsistencies, and help ensure accurate payment. It also provides a detailed record of the services you provided on each date of service, a requirement that many auditors request to substantiate billing claims and processes.

By mastering the 8-minute rule, therapists can focus more on delivering quality care to their patients and less on the intricacies of billing.

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