Pixel pitch gives you another way to estimate sensor size.

For an 8 MP sensor with a 4:3 aspect ratio, the pixel dimensions are approximately 3264 × 2448 pixels. If each pixel is about 1.5 µm wide, then the sensor dimensions are roughly:

• width: 3264 × 1.5 µm ≈ 4.9 mm
• height: 2448 × 1.5 µm ≈ 3.7 mm

That gives an area of about 18 mm².

The other estimate starts from the previous sensor area and the claimed increase. If the old sensor was about 15.5 mm², then a 15% increase gives:

15.5 × 1.15 ≈ 17.8 mm²

Those two independent estimates are close, which suggests the result is reasonable.

So yes: if you already know the new area and the aspect ratio, you can derive width and height from those alone. Pixel size is useful because it provides a separate cross-check using resolution × pixel pitch.

It’s only approximate, though, because real sensors are not perfectly filled with active pixel area; there can be gaps and inactive regions. More accurate methods use published crop factor/specifications or field-of-view measurements.