What does the DRG calculator do?

It takes the principal diagnosis and the secondary diagnoses of an inpatient stay, applies the CMS CC/MCC lists and the CC exclusion list for that principal diagnosis, and names the medical MS-DRG the stay groups to. It also shows which secondaries counted, which were excluded and why, the DRG family with relative weights, and what a documented CC or MCC would change.

Yes. The principal diagnosis plus up to 5 secondaries per check, with the complete CC/MCC and exclusion logic and no account required. The paid workspace takes the whole stay, up to 50 secondaries, and carries the same codes into the conflict check, Medicare coverage policy and HCC scoring.

Does it group surgical DRGs?

No. A stay with an operating-room procedure groups on the ICD-10-PCS procedure, and this calculator does not take procedures. It covers the medical DRGs, which are assigned from diagnoses alone. Newborn, HIV and pre-MDC cases depend on facts it does not take either, and it says so rather than guessing.

Which CMS version does it use?

The MS-DRG definitions manual CC/MCC lists and the IPPS Table 5 relative weights for the current fiscal year. Both versions are printed under every result, and the data-freshness badge at the foot of the page shows the release loaded.

Free tool

Free DRG calculator

Enter the principal diagnosis and the secondaries with their POA indicators, and get the medical MS-DRG the stay groups to: which secondaries count as a CC or an MCC once the CMS exclusions for that principal are applied, the DRG family with its weights, and what a documented CC or MCC would be worth. No signup, no card, no email.

Free for the principal plus 5 secondaries. We do not store what you enter, and please do not enter patient identifiers — we do not need them and do not want them.

How the DRG is assigned

1The principal diagnosis picks the MDC and the DRG family. Pneumonia lands in MDC 4 and the 193–195 family; the calculator reads the family from the CMS principal-diagnosis collections.
2Each secondary is checked against the CC and MCC lists, then against the exclusion list for the principal. A secondary that is on the CC list but excluded for this principal does not count, and the result says which.
3POA and hospital-acquired conditions are applied. A CC or MCC that was not present on admission and falls in a diagnosis-only HAC category is set aside, exactly as the grouper does.
4The highest counting secondary decides the split. One reportable MCC puts the stay in the with-MCC DRG; the result shows the weight gap to the next split so a CDI query is a decision, not a hunch.

Common questions

What does the DRG calculator do?: It takes the principal diagnosis and the secondary diagnoses of an inpatient stay, applies the CMS CC/MCC lists and the CC exclusion list for that principal diagnosis, and names the medical MS-DRG the stay groups to. It also shows which secondaries counted, which were excluded and why, the DRG family with relative weights, and what a documented CC or MCC would change.
Is it really free?: Yes. The principal diagnosis plus up to 5 secondaries per check, with the complete CC/MCC and exclusion logic and no account required. The paid workspace takes the whole stay, up to 50 secondaries, and carries the same codes into the conflict check, Medicare coverage policy and HCC scoring.
Does it group surgical DRGs?: No. A stay with an operating-room procedure groups on the ICD-10-PCS procedure, and this calculator does not take procedures. It covers the medical DRGs, which are assigned from diagnoses alone. Newborn, HIV and pre-MDC cases depend on facts it does not take either, and it says so rather than guessing.
Which CMS version does it use?: The MS-DRG definitions manual CC/MCC lists and the IPPS Table 5 relative weights for the current fiscal year. Both versions are printed under every result, and the data-freshness badge at the foot of the page shows the release loaded.

What it does not do

Surgical grouping. An operating-room procedure moves a stay to a surgical DRG on the procedure, and this calculator takes diagnoses only. Look the procedure up in ICD-10-PCS.
Payment. A relative weight is not a dollar amount. The hospital’s base rate, wage index and add-ons turn it into one, and none of those are here.
Your encoder. This is the CMS logic applied to the diagnoses you typed. The grouper in your encoder has the whole record, and it wins.

The MS-DRG reference lists every DRG with its weight and length of stay, and the free claim scrubber checks the same diagnoses for Excludes1 conflicts and sequencing errors before the claim goes out.