Calculating area, length, width, etc

[Hikki-Jin]

All right, well, admittedly math has never been my strong suit...

The darker green region in my map (obviously a wip) is ~709440px (according to Photoshop’s histogram tool). At its widest points, the region is ~1250px (east-west) and ~820px (north-south).

Say the region is ~23,648mi2 in area… That would work out to 30mi per pixel, right? (709440/23648 = 30 or 709440/30 = 23648)

So, then, that would mean that the region is ~41.7 and ~27.3 miles, in width and length respectively. (1250/30 = 41.66 and 820/30 = 27.33)

Is that all correct?

Because it seems strange… Wales, for example, runs about 170 miles (north-south) and 60 miles (east-west), with a total area of ~8,000mi2… How can the length/width of my region be much smaller than Wales, yet have a total area that is much larger?
Apparently, my ~23,648mi2 region could somehow fit within the boundaries of square that’s 100 x 100 miles, that is to say 10,000mi2 in area… but that can’t be right, can it? I must be doing something wrong here.

[Midgardsormr]

30 square miles per pixel. So each pixel is 5.47 miles wide and 5.47 miles long. 228 mi x 150 mi yields a bounding box of 34,200 square miles. The Welsh bounding box, assuming 170 x 60 miles is 10,200 square miles, which jives with the approximation of your numbers.

[Hikki-Jin]

Ohhhh. Okay, I see now. Thank you.

[Azélor]

Your numbers are probably right only if your using an equal area projection.
But since I assume your either using Mercator or Equirectangular: the value of each pixel in size decreases as the latitude increases.

So, if your want to know the exact size without distortion, use an equal area projection like Hammer or Moldweide. Any equal area will do for this but they tend to deform the shapes.