Quick takeaway: This CDR calculator returns two different results from six clinician-assigned ratings. Global CDR ranges from 0 to 3; CDR Sum of Boxes (CDR-SB) adds the ratings and ranges from 0 to 18.
How to use the CDR calculator
Enter the six box scores from a completed clinical assessment: memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care. Check the official CDR scoring table when assigning ratings. Personal Care has no 0.5 rating.
Global CDR and sum of boxes
The sum is straightforward:
CDR-SB = M + O + JPS + CA + HH + PC
Global CDR follows rules with memory as the primary category. It is not the sum divided by six. For example, memory 0 with impairment in at least two other domains gives Global CDR 0.5. Memory 0.5 with at least three other domains rated 1 or higher gives Global CDR 1. See the published scoring rules for the remaining majority and tie rules.
Worked example
Suppose a clinical assessment records memory 1, orientation 1, judgment 1, community affairs 1, home and hobbies 0.5, and personal care 0.
CDR-SB = 1 + 1 + 1 + 1 + 0.5 + 0 = 4.5 out of 18. Three secondary domains match memory, so Global CDR = 1, the mild dementia scale label. The sum of 4.5 and global score of 1 describe the same ratings in different ways.
Evidence note: Knight ADRC's algorithm guidance explains that CDR was developed for symptomatic Alzheimer disease and unusual box combinations can produce inappropriate global results. Clinical judgment remains necessary.
Common Mistakes
- Treating CDR-SB as Global CDR or converting a sum directly into a dementia stage.
- Selecting 0.5 for Personal Care, which is not a valid box score.
- Entering guesses instead of ratings from a clinical assessment.
- Including functional difficulty caused by physical illness in ratings intended to reflect cognitive decline.
This is a scoring reference for assessed ratings. It does not establish a diagnosis or replace a clinician's assessment.