Image Calculators | DPI, Pixels, Print Size and File Size | imgmuto
Calculate DPI, pixels to inches and centimeters, print size, aspect ratio, megapixels, raw image bytes, and convert KB to MB. Runs in your browser.
8 tools
Last updated 28 September 2026
Pick the number you actually need
Each calculator here answers one specific question, and choosing the right one saves a wrong answer. Working out how large a photo prints is different from checking whether a file fits a form, and both are different from translating a number between units. Start from the decision you have to make, then use the calculator that matches it. All of them run in your browser and update as you type, so nothing is uploaded and nothing is stored.
Pixels, resolution, and physical size
Pixels divided by resolution gives physical size, and that one relationship explains most of what people look up. At 300 PPI a 4 by 6 inch print is 1,200 by 1,800 pixels, an 8 by 10 is 2,400 by 3,000, and a US passport photo is 600 by 600. Drop to 150 PPI and the same print needs half the pixels, which is fine for a poster seen from across a room. The catch is that CSS treats 96 pixels per inch as a fixed reference, so a number measured for a screen is not a number measured for paper. Use the DPI calculator to solve for whichever value you do not have, the pixels to centimeters converter for metric work, and the print size calculator for the largest size a file supports.
Proportions and resolution totals
Aspect ratio locks the shape of an image so a resize never stretches it. The ratio is width divided by height, reduced to its simplest form, so 1,920 by 1,080 becomes 16 by 9 and 1,080 by 1,080 becomes 1 by 1. Megapixels is width times height in millions, which is the figure camera manufacturers quote: a 12 megapixel sensor produces 4,000 by 3,000 pixels. Megapixels measure pixel count only, so they say nothing about how much usable detail those pixels captured. The aspect ratio calculator reduces a ratio, inverts one, and finds the missing side, while the megapixel calculator converts dimensions in both directions.
File size: two different questions
There is an exact answer for raw pixel data and no exact answer for a compressed file, and treating them as the same question causes most of the confusion. Raw size is width times height times bits per pixel divided by eight, which is a ceiling rather than a prediction. Converting between KB and MB is different again: it changes the number you read without touching a single byte, and the result depends on whether the system you are dealing with counts in 1,000 or 1,024. The image file size calculator gives the exact raw figure, the KB to MB converter shows both unit conventions, and the image size checker reads the real size of a file you already have.
Turning a number into a file
Calculators answer questions, but most file problems still need an actual file changed. Once you know the target size, the next step is re-encoding rather than more arithmetic, which is what the compress to 1MB tool does by searching for the best quality that still fits. Once you know the print size, resize to a print preset. And if a number looks wrong, check it against the photo print size chart before trusting it.
- Aspect Ratio Calculator | Simplify Width by Height | imgmutoAn aspect ratio only means something once it is reduced, so 1,920 by 1,080 becomes 16 by 9 rather than a pair of large numbers. This calculator does that reduction, and inverts it too: give it a target ratio and one known dimension, and it returns the other side without changing the proportions.Open tool
- DPI Calculator | Check Image Print Resolution | imgmutoPrint DPI is not a quality setting you apply to a file. It is a number that falls out of two other numbers: the pixels you have and the physical size you want. This calculator solves for whichever of the three you do not have, so you can go from a photo size to a resolution, or from a resolution to the pixels a print shop will ask for.Open tool
- Print Size Calculator | Max Print Size Free Online | imgmutoEvery print size question has a ceiling, and that ceiling is set by your pixel count rather than by the paper you can buy. This calculator finds it: enter both dimensions and a target resolution, and it returns the largest width and height that still looks sharp, in both units, so you can check it against a standard frame before ordering.Open tool
- Image File Size Calculator | Raw Pixel Data Bytes | imgmutoThere is an exact answer for raw pixel data and no exact answer for a compressed file, and confusing the two is the most common mistake in file size planning. This calculator gives you the exact raw figure, shows the arithmetic behind it, and is explicit that your final JPG or WebP will land somewhere below it. Use it to plan storage, not to promise a byte count.Open tool
- Megapixel Calculator | Pixels to Megapixels | imgmutoMegapixels are a camera specification, not a quality score, and the number only means something next to the sensor and lens behind it. This calculator converts dimensions both ways, so you can check what a sensor size spec means in pixels, and it pairs that with the print size and crop factor that the same pixels imply.Open tool
- Pixels to Inches | Calculate Print Size Free | imgmutoA pixel count on its own does not tell you how big a print will be, so this converter makes the resolution the deciding input rather than an afterthought. Enter pixels and a resolution, and it returns the physical size in inches, plus the metric equivalent. The worked examples cover the resolutions cameras and phone screenshots actually produce.Open tool
- Pixels to CM | Convert at Any PPI Free Online | imgmutoMetric print work needs centimeters, and the conversion hinges entirely on resolution. This converter takes pixels and a resolution and returns the metric size, so a figure laid out for an A4 page at 300 PPI means the same thing as a photo you are about to print. The reference table covers the pixel counts that A4, A3, and phone photos actually use.Open tool
- KB to MB Converter | Decimal and Binary Units | imgmutoA KB to MB converter is only as useful as the unit convention behind it, so this one shows both. Choose decimal, where 1 MB is 1,000 KB, or binary, where 1 MiB is 1,024 KiB, and the result and the unit labels change to match. It runs in your browser and never touches your file.Open tool
Frequently asked questions
How many pixels do I need for a sharp 4 by 6 print at 300 DPI
1,200 by 1,800 pixels. At 300 dots per inch, width is pixels divided by DPI, so 1,200 divided by 300 is 4 inches and 1,800 divided by 300 is 6 inches. For an 8 by 10 print at 300 DPI you need 2,400 by 3,000 pixels. The print size calculator gives the largest size for any file.
What is the difference between KB and KiB
KB usually means 1,000 bytes and KiB means 1,024 bytes. The same distinction applies to MB and MiB. Storage manufacturers use the decimal system while older systems report the binary one, which is why a marketed 1 TB drive appears as about 931 GiB. The KB to MB converter shows both readings side by side.
How do I estimate the size of a JPG before I export it
You cannot do it exactly, because compressed size depends on the content and the quality setting. The image file size calculator gives the exact raw pixel figure as a ceiling, and for an actual byte target use a target size compressor, which re-encodes until the file fits.
What aspect ratio should I use for a 1920 by 1080 thumbnail
16 by 9. The width divided by height is 1.78, and reducing the pair gives 16 by 9. Use the aspect ratio calculator to find the height that matches a chosen width at that ratio before resizing, so frames and thumbnails keep clean proportions.
Why does DPI matter for print but not for screens
DPI describes how many pixels map to one inch of paper, so a printer needs it to set a physical size. Screens show pixels directly, so display size depends on pixel dimensions alone. A 1,920 by 1,080 image is full HD on screen at any DPI value. Check the arithmetic with the DPI calculator.
Which calculator helps me meet a 1MB upload limit
Use the image file size calculator to see where you stand, then open the compress image to 1MB tool. It searches for the highest quality that still fits under the stated byte limit, runs in your browser, and processes several files at once.