Delta T Calculator
Calculate temperature split and diagnose system performance
Free tool for field decisions
Why this tool matters
Solve the calculation or lookup now, then use the demo to see how the answer can stay visible on the morning operating board.
Next best step
Use the result in the field, then see the interactive demo when you want the answer to stay visible after this visit.
What is Delta T?
Delta T (ΔT) is the temperature difference between supply and return air.
Formula: ΔT = Return Temperature - Supply Temperature
Cooling Mode: Target 18-22°F split (lower = problem)
Heating Mode: Target 40-70°F split (higher temp rise)
Delta T Guidelines
❄️ Cooling Mode
✓ Good: 18-22°F
⚠ Low: < 15°F
✗ Very Low: < 12°F
⚠ High: > 25°F
🔥 Heating Mode
✓ Good: 40-70°F
⚠ Low: < 35°F
✗ Very Low: < 25°F
⚠ High: > 80°F
Automatic Performance Tracking
AssureStep AssureStep gives you unlimited equipment tracking, CSV import, tracks trends, and alerts you to declining system performance.