How to crop an image to a specific size

You crop an image to a specific size in two steps: first you crop it to the right aspect ratio, such as 3 : 2, and then you resize it to the target width in pixels. You can do it online in your browser with the Photopea editor, with nothing to install and no registration. This article walks you through it step by step and adds a table of image sizes for email plus our measurements of how large a file can reasonably be.

Key takeaways

1. Cropping removes the edges of an image, resizing shrinks the whole image. To hit an exact size you need both.
2. The simplest order is to crop to the aspect ratio first and then change the width. The height follows automatically and the image does not get distorted.
3. Images in the same email row must share the same aspect ratio and width, otherwise the row will not line up.
4. Prepare the file about twice as wide as its space in the email. It then stays sharp on Retina displays.
5. Save photos as JPG at 70 to 80% quality. Quality 100% makes the file up to seven times larger.
6. WebP does not belong in email, because Outlook for Windows does not display it and Gmail converts it to JPG.

In short: what you need, which size to choose, how long it takes and what can go wrong

• What you need: the image on your computer and a browser. Photopea works online with nothing to install and no registration.
• Which size to choose: multiply the width of the space in the email by two, and the aspect ratio sets the height. Three images side by side in a 650 px email need 400 px each.
• How long it takes: about two minutes per image, and a whole set of newsletter images in under a quarter of an hour.
• What can go wrong: an uneven row, distorted or blurry photos and needlessly large files that load slowly.

What has changed since publication: This article was first published in September 2021. In October 2026 we updated it for the current version of Photopea (a new landing page, language set by the browser, the Save for web window), added a faster method using a fixed aspect ratio, a table of image sizes for email, the advice to prepare images at double size for Retina displays and our own file size measurements. We originally recommended preparing images at exactly their display size. Today we recommend double.

Why crop images to the same size

Cropping an image means removing its edges so that it has the required aspect ratio or dimensions without being distorted. Resizing, on the other hand, scales the whole image up or down while keeping all of its content. To get exact pixel dimensions, such as 450 × 300 px, you usually need both.

Sometimes you get lucky and all your images are already the same size, so there is nothing to edit. In other cases you need to crop an image to a specific size. A typical example is placing three images side by side in one email row. The email editor gives each image the same width but keeps the height of the original. A portrait photo next to a landscape one then throws the whole row off.

The aspect ratio is the ratio of an image's width to its height. For example, 3 : 2 means the image is half as wide again as it is tall. Images with the same aspect ratio and the same width automatically have the same height. The whole method is built on this.

Which image size to choose for email

Image dimensions depend on the email width and the margins you have set. The default email width in Quanda is 650 px, and you can change it with the gear icon in the right panel of the email editor. Subtract the page margins and the gaps between columns (16 px in the default settings) from the email width and divide the result by the number of images in the row.

For three images side by side in a 730 px email, the calculation is (730 − 4 × 16) / 3 = 222 px. That is how much space each image gets.

The calculation assumes the default 16 px margins and gaps. If you have changed them, use your own values. The guide Image size in an email campaign covers the details.

Why double and not the exact size

A Retina display is a high pixel density screen that uses two or three physical pixels for every point of the image. An image exactly 222 px wide gets stretched across 444 display pixels and looks soft. An image 450 px wide stays sharp, and the email editor scales it down to the 222 px space on its own.

Data on where people open their emails shows this is no edge case. According to Litmus, in July 2026 Apple devices accounted for 62.26% of roughly a billion tracked opens, Gmail for 27.03% and Outlook for 5.83%. The Apple figure includes automatic opens by Mail Privacy Protection, so the number of real readers is lower. Even so, iPhones and Macs with Retina displays make up a large share of the audience.

How to crop an image to a specific size in 7 steps

We will demonstrate the process in the Photopea editor on a photo we need for a row of three images in a 730 px email, so the target size is 450 × 300 px. Photopea is an online image editor developed since 2013 by a developer from the Czech Republic. It runs in the browser and works much like Photoshop. The basic version requires no registration and no fee, and it shows ads.

1. Work out the target image size and its aspect ratio, for example 450 × 300 px and a ratio of 3 : 2.

2. Open the Photopea editor at photopea.com and click Start using Photopea. The editor language follows your browser language. If you want a different one, switch it under More, Language.

3. Click Open From Computer and select the image you want to crop. You can also drag and drop the image into the editor window.

4. Choose the Crop Tool in the left panel, set Fixed Ratio 3 : 2 in the top bar, move the crop box over the part you want to keep and press Enter. You can also select the Crop Tool with the C key. Instead of typing the ratio, you can pick the 3 : 2, 4 : 3, 1 : 1 or 16 : 9 preset from the dropdown.

   

5. Go to Image, Image Size, type 450 in the Width field and click OK. The height is calculated automatically. The chain between Width and Height must stay locked, otherwise the image would get distorted.

   

6. Go to File, Export as, JPG, set the quality to 70 to 80%, check the file size and click Save. The Save for web window shows the file size in the bottom left corner. The image is saved to the downloads folder on your computer.

   

7. Edit the other images for the same row in the same way, insert them into the email editor and send yourself a test email. You can insert an image into the email from your computer or by using the image URL from your website, as described in the guide Email editor of a simple email campaign.

Try an email with three images in Quanda

How to crop an image to exact dimensions when the images already share the same width

If your images are already resized to the same width and differ only in height, the original method with a fixed crop size comes in handy. Personally, I first change the overall size of the image and then crop it so that all three images end up with the same height.

1. Give all images the same width in the Image Size window, for example 450 px, and note down the height that is calculated for each one.
2. The smallest of these heights is the target height for all of them. The image with the smallest height is already done.
3. Open the other images, choose the Crop Tool and select Fixed Size instead of Fixed Ratio in the top bar. Type the target dimensions into the W and H fields, for example 450 and 300.
4. Position the crop box so that its width matches the width of the image and move it over the part you want to keep. Press Enter and save the image as JPG.

A fixed crop size works directly in pixels, so the image has to be resized to the target width first. For photos with a completely different aspect ratio, the 7 step method above is faster. For more detail on resizing, see the article How to resize an image online.

How large should the image file be

Pixel dimensions and file size are related, but they are not the same thing. File size also depends on the JPG compression quality. To get real numbers, in October 2026 we took one 1920 × 1279 px photo in Photopea and saved it at different widths and with different JPG quality settings.

The photo resized to 450 px wide is a tenth of the original size, and that is all you need for an email.

Going from 100% to 90% quality makes the file more than four times smaller, and from 100% to 70% roughly seven times smaller. The difference in photo quality is usually hard to spot on screen in an email. That is why we recommend 70 to 80% quality. Below 60%, photos with smooth gradients, such as a sky, may start to show blocky artifacts.

Tip: In Quanda we recommend keeping every image uploaded to a campaign under 2 MB. Based on our measurements, though, even a full width email image fits into roughly 100 kB. Smaller images load faster for recipients, especially on mobile data.

Which image format to choose

Format support across email clients is tracked by Can I email. According to it, Apple Mail displays WebP, but Outlook for Windows does not and Gmail converts it to JPG (as of October 2026). Support for other formats such as AVIF, SVG and HEIC is compared in the article JPG, PNG or GIF? Which image file type to use for email marketing.

What else you can use to crop an image

Photopea is not the only option. The same method, cropping to an aspect ratio and then changing the width, also works in tools you already have on your computer or phone.

Watch out: There are three common mistakes when preparing images for email. You drag an image by its corner without the aspect ratio locked and the image gets distorted. You insert a photo straight from the camera that is several thousand pixels wide and the email loads slowly. Or you put important text only in an image. Some recipients have image loading turned off, typically in corporate Outlook, and then never see the text in the image at all.

Tip: Give every image in Quanda an alternative text. After inserting an image into the email, enter it in the right panel in the image title field, and you can also style it with a font, size and colour. Recipients who have images turned off will see the styled text instead of the image. The whole procedure is described in Can't see images in an email? Styled alt text shows a headline..

Checklist before inserting images into an email

• Images in the same row share the same aspect ratio and width.
• The file is about twice as wide as its space in the email.
• Photos are saved as JPG at 70 to 80% quality, logos and graphics as PNG.
• No file is larger than a few hundred kilobytes, and definitely not over 2 MB.
• Every image has its image title filled in, which is its alternative text.
• The key message is also in the email text, not just in an image.
• I have checked the test email on both a computer and a phone.

Final thoughts

Cropping an image to a specific size takes two minutes: crop to the aspect ratio, change the width and save at a sensible quality. All that is left is to work out how much space the image has in the email and prepare it at twice that size.

For working with images across the whole email, where to get them and how to combine them with text, take the free online course Email Copywriting and Design That Gets Read. If you are stuck with images or with a whole campaign, book a free consultation or write to us at support@onquanda.com.

Good luck!