Design
DPI/PPI Calculator (Print Size ↔ Pixels)
Convert pixels and PPI to print dimensions, or calculate the pixels needed for a target print size. Compare horizontal and vertical effective PPI and read image dimensions locally in your browser.
About DPI/PPI Calculator (Print Size ↔ Pixels)
What this calculator measures
This tool calculates image pixels per inch (PPI) from pixel dimensions and finished print dimensions. It does not measure printer dot density, halftone screening, paper, or colour processing.
One inch equals 25.4mm. The formulas are PPI = pixels ÷ print size in inches and required pixels = print size in mm ÷ 25.4 × PPI.
Three calculation modes
- Pixels to print size: calculate output dimensions from pixels and PPI.
- Print size to pixels: calculate the whole-pixel dimensions needed for a target size and PPI.
- Effective PPI: calculate horizontal and vertical PPI separately from pixels and print dimensions.
Rounding and unequal axes
Required pixel dimensions are rounded to the nearest whole pixel. The detailed result recalculates effective PPI from those rounded dimensions, so it may differ slightly from the requested value.
If the image and print aspect ratios differ, horizontal and vertical PPI also differ. NanToo displays both and uses the lower one for its density guidance instead of hiding the difference in an average.
300 ppi is a reference, not a universal pass mark
Required density depends on the printing method, source image, paper, viewing distance, and the print provider's specification. The preset values are comparisons, not guarantees of output quality.
The 96 ppi preset reflects the CSS conversion 1in = 96px. It does not represent a display's physical pixel density.
Local image inspection and limits
JPEG, PNG, WebP, and AVIF files up to 10MB, 16,384px per side, and 40 megapixels can be inspected. The image stays in your browser; only its displayed width and height are copied into the calculator.
Embedded resolution metadata is not read. PPI is calculated from the image's pixel dimensions and the print dimensions that you enter.
Frequently asked questions
- Q. Are DPI and PPI the same?
- No. PPI describes how many image pixels are assigned to one inch. DPI describes dots produced by a printing device. This calculator reports PPI; DPI remains in the title because it is a common search term for this calculation.
- Q. Does 300 ppi guarantee a high-quality print?
- No single value guarantees quality. Source sharpness and compression, the printing method, paper, viewing distance, and the print provider's requirements all matter. Treat 300 ppi as a common close-viewing reference and follow the provider's specification.
- Q. Does changing resolution metadata to 300 add detail?
- No. Changing metadata without resampling does not add pixels or image detail. With the same pixel dimensions, selecting a higher PPI produces a smaller calculated print size.
- Q. Why are the horizontal and vertical PPI different?
- The image and print dimensions have different aspect ratios. Filling the print may stretch the image; preserving its ratio requires cropping or margins. The calculator shows both axes and uses the lower value as the effective PPI.
Questions or feedback? Contact NanToo
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