DPI Calculator

What Is a DPI Calculator?

A DPI Calculator is an online tool for determining the resolution of an image or printed output in dots per inch. By entering an image's pixel dimensions and physical dimensions, you can calculate the DPI required to produce that size.

The calculator can also work in reverse. If you know the image dimensions and target DPI, it can calculate the corresponding physical print size. Alternatively, you can enter a desired physical size and DPI to determine how many pixels are required.

Why Use the DPI Calculator?

DPI calculations are useful when preparing images for printing, scanning, publishing, photography and other workflows where digital image dimensions need to correspond to a physical output size.

How to Use the DPI Calculator

The calculator provides three calculation modes depending on the information you already have.

1. Choose a calculation type — Select Calculate DPI, Calculate Print Size or Calculate Pixels.
2. Enter the relevant dimensions — Provide the image's pixel dimensions, physical dimensions or target DPI according to the selected mode.
3. Select the appropriate unit — Physical dimensions can be entered in inches, centimetres or millimetres.
4. Calculate the result — Select the calculation button to display the resulting DPI, physical dimensions or required pixel dimensions.

How Is DPI Calculated?

DPI is calculated by dividing the number of pixels in an image dimension by the corresponding physical measurement in inches. For example, an image that is 3,000 pixels wide and intended to be printed 10 inches wide has a horizontal resolution of 300 DPI.

The same principle can be applied vertically. If an image is 2,000 pixels high and is printed at a height of approximately 6.667 inches, the vertical resolution is approximately 300 DPI. When width and height use the same proportional scaling, the image has the same effective resolution in both directions.

Calculating Print Size From DPI

To calculate physical print size, divide the pixel dimension by the target DPI. For example, 3,600 horizontal pixels at 300 DPI produce a physical width of 12 inches. Increasing the DPI while keeping the pixel count unchanged reduces the calculated physical print size.

Calculating Pixels From DPI and Print Size

When preparing an image for a particular physical output size, multiply the required width and height in inches by the target DPI. A 10 × 8 inch print prepared at 300 DPI requires 3,000 × 2,400 pixels.

DPI vs PPI

DPI stands for dots per inch and is traditionally associated with physical printing, where dots of ink or toner are placed on a page. PPI stands for pixels per inch and is more accurately used for digital images and display pixel density. Despite the technical distinction, DPI is commonly used in image-editing and printing software to describe an image's intended print resolution.

A DPI value does not by itself increase the number of pixels in an image. Changing the resolution metadata can alter the calculated physical print dimensions without adding image detail. To increase the actual detail available for a particular print size, the image needs sufficient pixel dimensions.

Frequently Asked Questions