What are the maximum image dimensions that can fit in X megapixels? How big can we print it?
What image size do we get if we buy a 50 megapixel camera? Or with any 50 megapixel image?
The dimensions of its shape depend on the Aspect Ratio.
The calculator below shows your request and also automatically adds results for a few standard aspect ratios (1:1, 4:3, 3:2, 16:9). These rounded nominal values may not precisely match your sensor dimensions, but your first request can use an Aspect Ratio more precise than the nominal 3:2 or 4:3.
but which are just rounded approximate nominal values. Or preferably more precise, it can be the exact corresponding divided number (image width/height, dimensioned as pixels or mm or inches) like the 1.5 or 1.3333 or 1.7778 ratio. Example: for 4:3 aspect, 4/3 = 1.3333. But it can be the more exact number, like maybe 1.327:1. It is Not necessary to enter the :1 here (:1 is assumed if not), but you can enter it or not, or you can enter the format like 4:3. For an actual real sensor, the actual precise value (like 1.327 or 1.503) may compute more precisely. More about aspect ratios.
Megapixels are exactly computed by image dimensions in pixels, megapixels = Width × Height. 6000×4000 = 24,000,000 pixels, = 24 megapixels. Megapixels use the conventional 1K = 1000, and NOT the 1K = 1024 used by memory chips.
Aspect Ratio is exactly computed by image dimensions in pixels, Aspect Ratio = Width / Height. 6048 / 4024 is 1.503 : 1.
Your results will come out closer if entering your actual real numbers instead of the rounded camera specifications.
But there are ifs and buts about everything, so this is trying to explain why the result megapixels may not exactly match your camera's specified megapixels. Three values of pixel dimensions may be shown, in the order of:
1. Exact computed dimensions (matches specified megapixels exactly, even if pixels cannot be fractional). Aspect Ratio can be entered in formats such as 1.3333 or as 4:3
2. So dimensions are also rounded to whole pixels, necessary for real pixels, but which changes megapixels a little. One pixel difference of width might affect a few thousand rows of height.
3. Cameras create pixel dimensions that are evenly divisible by 8 (I will call it Div8, and is only size shown if already Div8 is specified). But resampled or cropped images might have any dimensions, likely Not divisible by 8.
Div8 - Images resized in photo editors can be any dimensions, but camera sensors actually use pixel dimensions which are evenly divisible by 8, no doubt to match the JPG 8x8 compression blocks (I'll call that value Div8 here). Image pixel dimensions created by the actual camera are optimally Div8, however specifications for megapixels or aspect ratio are rounded. But pixel dimensions of images cropped or resampled in your editor have low odds to be evenly divisible by 8 (which still works).
There are two calculator options, and the results for each case are:
Since images cannot be dimensioned in fractions of pixels, the result rounded to whole numbers is then shown (in green). Adding or Subtracting one pixel to width or height can be thousands of pixels in the other dimension, so the rounded result necessarily can affect the megapixel total somewhat. And then actual camera sensors typically round to multiples of 8 pixels (evenly divisible by 8). The camera specifications round off megapixels, but the precise value is image width × height in pixels. Likewise, Aspect ratio is rounded to a nominal value too, but the precise actual value is image width / height, in pixels.
If checking that the calculator matches your cameras Div8 dimensions, the specifications for megapixels and aspect ratio are rounded nominal numerals which will be close, but might not compute the exact precise image size in pixels (due to rounding - camera specifications are rounded values.) If not exact, the best try for the significant digits is to first enter the second option of actual sensor dimensions in pixels instead of Megapixels to compute the actual precise megapixels and aspect ratio values for your camera. Dividing Width by Height of either camera image pixels or sensor mm provides actual aspect ratio, however both sensor mm and aspect ratio are rounded in specifications, and probably will NOT exactly agree with each other.
Otherwise, Megapixels will work fine, and even better if you enter accurate higher precision for the actual megapixels and aspect ratio. Since pixel dimensions are typically four significant digits, then to reach that same four-digit precision again, enter all values to at least four significant digits, if applicable. Four digits total are usually enough, but sometimes five digits can be better on Aspect Ratio. The Image Size option does compute sufficient precision from your dimensions. You can see in the initial default example, that 1.503 computes better than the nominal 1.5 below it (unless 1.5 happens to be the actual precise value).
Again, camera megapixels and aspect ratio are said as nominal rounded values. But these two values are just a multiplication and a division of the pixel dimensions, and as explanation of the precision offered, the second Image Size option was added to show those actual more precise computed values. They also show the difference from the nearest standard nominal aspect ratio (if in range). The few tenths of a percent of difference is not a big deal in practice. See the Aspect Ratio page.
The goal is to compute maximum dimensions of a specific aspect ratio that matches the specified megapixels. Megapixels is sensor Area (in units of pixels). Pixels are the only units used. The calculator computes the Width x Height image pixel dimensions of various aspect ratios that match the megapixels that you specify.
The terms kilobytes and megabytes and gigabytes were corrupted to mean multiples of 1024 bytes, necessarily used for memory chip sizes (including memory cards, USB flash drives and SSD, which are all memory chips which truely use 1024 byte units that are required by memory addressing). But sadly, computer operating systems commonly use the 1024 base for file sizes, which is unnecessary and counter-productive. The standard SI term mega means millions, defined as multiples of 1000. So mega in megapixels still correctly means 1000s, same way as humans count things. Same true also for manufacturer's hard disk specifications in gigabytes (units of 1000s), except our computer operating systems still sadly also refer to size of hard drives and files as multiples of 1024, but which do not use memory binary addressing, so no 1024 complications. A 4 GB hard drive is sold as 4,000,000,000 bytes, which the operating system calls 3.725 GB, but which in fact is in fact exactly 4,000,000 bytes. The term mega is correctly units of 1000, except actual memory devices do their own thing, necessarily using 1024 units.
Math is precise, but Real World is sometimes less so: If checking the calculator against your camera, realize that cameras round their specifications, which affects precise calculations. For example, a Nikon D800 camera specifies 36.3 megapixels and we assume a DSLR nominal 3:2 aspect ratio. That computes 7376 x 4920 image size. Close, but its actual is 7360x4912 pixels which computes 36.152 megapixels and 1.498 aspect ratio, which does then compute the correct image size. If you enter the actual correct numbers, the calculator should show the exact dimensions.
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