REDCap Calculated Fields

A Practical Guide to Scoring, Dates, and Dynamic Values


Automatically calculate values based on data entered in your project

Calculated fields allow REDCap to automatically compute values in real time using data from other fields. They are commonly used for scoring instruments, calculating age or time intervals, and generating derived variables for analysis.

Core Principle: Calculated fields always return a numeric value based on a formula using other fields.
⚠️ Important: Calculated values are not automatically saved for existing records when you change a formula. You must run Data Quality Rule H to update stored values.

What Calculated Fields Do

  • Automatically compute scores
  • Calculate age or time differences
  • Generate derived variables
  • Reduce manual calculation errors
✅ Best Practice: Use calculated fields for simple, real-time calculations—not complex data processing.

Calculation Syntax

Basic format:

[field1] + [field2]

Examples:

[bp_sys] + [bp_dia]
[bmi_weight] / ([height]^2)
if([age] > 65, 1, 0)
Tip: Use square brackets for all variables.

Common Functions

  • sum()
  • mean()
  • min(), max()
  • round()
  • if()
sum([q1],[q2],[q3])
round([value],1)
if([score] > 10, 1, 0)

sum() vs +

Method Behavior
+ Fails if any field is blank
sum() Ignores blanks
⚠️ Important: Choose based on scoring rules.

Working with Dates

datediff([dob],[visit_date],"y")
datediff("today",[visit_date],"d")
  • y = years
  • d = days
  • M = months
⚠️ Important: “today” updates each time the record is opened.

Checkbox Calculations

if([exercise(1)] = 1, 1, 0)
⚠️ Important: Checkbox values are binary (0/1), not choice codes.

Real-World Examples

Total Score

sum([q1],[q2],[q3],[q4])

Age

datediff([dob],"today","y")

Eligibility Flag

if([age] > 18,1,0)

Updating Values (Rule H)

  1. Go to Data Quality
  2. Run Rule H
  3. Click “Fix calcs now”
⚠️ Important: Updates ALL records.

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Common Mistakes

  • ❌ Using text instead of numeric output
  • ❌ Not running Rule H
  • ❌ Using checkbox incorrectly
  • ❌ Overcomplicating formulas

Best Practices

  • Keep formulas simple
  • Use sum() when appropriate
  • Test thoroughly
  • Avoid heavy use in large projects