Calculate wound surface area in cm² from length and width (L × W or ellipse), solve for a missing dimension, or track area reduction between visits.
Wound Surface Area Formula
The calculator uses one of two area methods, or compares the measured areas from two visits.
- L = greatest length of the wound (cm)
- W = greatest width perpendicular to L (cm)
- π/4 ≈ 0.785398 is the ellipse correction factor (Kundin)
- Abaseline = wound area at the first visit (cm²)
- Acurrent = wound area at the current visit (cm²)
Length and width must be measured perpendicular to each other on the same visit, with the patient in the same position. The result is a 2-D charting area only. Depth, undermining, and tunneling are documented separately. Use cm for clinical records; mm and inches are converted automatically.
Interpreting Change Over Time
Percent area reduction is a tracking measure, not a universal healing verdict. Interpret measurements with the wound type, tissue condition, depth and the treating clinician’s assessment. A change in projected area alone does not diagnose healing or infection. Keep the measurement method and positioning consistent across visits.
Quick area conversions for common rectangular dimensions (L × W method):
| Length × Width | Rectangular (cm²) | Ellipse (cm²) |
|---|---|---|
| 2.0 × 1.0 cm | 2.00 | 1.57 |
| 3.0 × 2.0 cm | 6.00 | 4.71 |
| 4.2 × 2.8 cm | 11.76 | 9.24 |
| 5.0 × 4.0 cm | 20.00 | 15.71 |
| 8.0 × 6.0 cm | 48.00 | 37.70 |
Example and FAQ
Example. A pressure injury measures 4.2 cm long by 2.8 cm wide at baseline. Four weeks later it measures 3.1 cm by 2.0 cm. Using length × width:
- Baseline area = 4.2 × 2.8 = 11.76 cm²
- Current area = 3.1 × 2.0 = 6.20 cm²
- % reduction = (11.76 − 6.20) / 11.76 × 100 = 47.3%
The measured area reduction is 47.3%. Interpret that change using the wound type, the full clinical assessment, and the treating clinician’s protocol; this percentage alone does not establish that the wound is on track.
Which method should you use? Length × width is a simple ruler estimate and can overestimate irregular wound area. The ellipse method (× π/4) assumes an oval shape. Pick one and use it consistently across visits.
How do you measure length and width? Use the longest dimension as length, then measure width at a 90° angle to that line, at the widest point. Many clinicians use a head-to-toe convention for length on the trunk and limbs.
Does this replace planimetry or photo tracing? No. Digital planimetry is more accurate for irregular wounds. The L × W and ellipse methods are quick bedside estimates suitable for routine charting.
