CPT code 77300: Dosimetry calculation, basic, per calculation2026 Medicare rate & RVUs

Medicare pays $67.14 for 77300 nationally in the office. Local office rates run $60.04–$88.95.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What 77300 covers

This service calculates a radiation dose parameter needed to deliver the physician's prescription, such as the monitor units or treatment time for a beam at a specified depth. Other examples include an off-axis factor, tissue inhomogeneity correction, or gap calculation between adjacent fields. A medical dosimetrist or medical physicist typically prepares the calculation in a hospital radiation oncology department or freestanding treatment center; the radiation oncologist reviews and approves the result.

Report a unit for each distinct physician-prescribed calculation, not automatically for each field. A later plan change supports another unit only when it requires a separately prescribed and documented calculation. Retain the prescription, calculation record, and physician approval. Calculations included in a teletherapy isodose plan or an IMRT plan are not separately reported as 77300 for that plan. CMS prices professional and technical components separately: modifier 26 identifies the physician's professional work, modifier TC identifies the equipment and staff component, and an unmodified claim represents both components.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 77300 pays more and less

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 of 109 payment localities

77300 rates by state

Office rate range in each state. Select a state to see its payment localities.

How the 77300 rate is calculated

Each of 77300’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for 77300

The CMS indicators that decide how 77300 is paid alongside other services.

What modifiers do to the payment

When to use modifier 26

77300 compared with similar codes

How to choose

77306Radiation planSimple teletherapy plan

77306 covers a simple teletherapy isodose plan, including its basic calculations. Report 77300 for a distinct physician-prescribed calculation rather than separately reporting a calculation included in that plan.

77307Isodose planningComplex teletherapy plan

77307 covers a complex teletherapy isodose plan, including its basic calculations. Use 77300 for a distinct physician-prescribed calculation outside that plan.

77331Radiation dosimetrySpecial measurement

77331 covers special dosimetry that measures dose, such as with a diode or thermoluminescent dosimeter. 77300 is a calculation, not a physical measurement.

77301IMRT planningDose optimization and volume analysis

77301 covers IMRT planning and its included dose calculations. Do not separately report 77300 for calculations included in that IMRT plan.

Codes related to 77300

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates