Most lung cancers double in volume within 20–400 days. Very fast growth (under 20 days) suggests infection, while no growth over 2 years for a solid nodule usually indicates a benign lesion. Volumetry is more precise than diameter.
How to use the Lung Nodule Growth Rate Calculator
- First diameter
- Second diameter
- Days between scans
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the average nodule diameter on each scan and the days between them.
Inputs explained
| Field | What to enter |
|---|---|
| First diameter | In mm |
| Second diameter | In mm |
| Days between scans | A number |
What each result means
- First volume = pi÷6×[First diameter]^3
- Second volume = pi÷6×[Second diameter]^3
- Volume change = ([Second volume]÷[First volume] – 1)×100
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Volume = π/6 × diameter³
Volume doubling time (days) = days × ln 2 ÷ ln(V₂ ÷ V₁)
< 400 days: suspicious for malignancy · 400–600 indeterminate · > 600 days usually benign
Worked example
Inputs — First diameter: 6 mm; Second diameter: 7.5 mm; Days between scans: 120.
Results — First volume = 113 mm³; Second volume = 221 mm³; Volume change = 95 %; Volume doubling time = 124 days.
Key terms
- VDT
- Volume doubling time.
Frequently asked questions
What doubling time suggests cancer?
20–400 days for solid nodules.
Why use volume rather than diameter?
A 26% increase in diameter already doubles the volume.
What if the nodule shrinks?
Shrinking nodules are usually inflammatory or infectious.