An upload form asks for a photo "1200 pixels wide" or "600 × 600 px". A website wants images no bigger than 1600 pixels. Or you just want a set of photos small enough to send without a dozen huge attachments. This guide explains what resizing a photo actually changes, then shows how to resize one photo or a whole batch with Convert Cat, our photo and PDF converter for iPhone and iPad.
What "resize" means
A photo is a grid of pixels, and a photo from the camera has millions of them. Resizing changes how many there are: the width and height in pixels. There are three common ways to ask for a size:
- By the long side. "1600 px long side" means the longer edge becomes 1600 pixels and the shorter edge follows, so the shape stays the same.
- By percent. 50% halves both the width and the height.
- Exact width and height. "1080 × 1080" means exactly that many pixels. If the photo's shape is different, something has to give, either cropping or stretching.
Fewer pixels also makes a smaller file, which is why resizing is one of the ways to shrink a photo.
Resize a photo, step by step
- Open Convert Cat. The first time, it asks "What are you making?": tap Convert & PDFs, and it opens there from then on.
- Tap Choose Photos and pick one photo or as many as you like. For pictures in iCloud Drive or Files, tap Choose Files instead.
- Tap Resize. It's in the list of things to do with your photos, with the note "Email, social, percent or exact pixels". If every photo you picked is an iPhone photo (HEIC), a quick Convert to JPEG button comes first and the list sits under "Or something else".
- Pick a size under Pixels (see below). The panel at the top shows the new size in pixels, such as "1600 × 1200 px", and about how big the file will be. With several photos, the pixel size shown is for the first one.
- Tap Resize. The button counts your photos, such as Resize 3 Photos.
- Save or send. On the result, tap a file to look at it, then tap Save to Photos, Save to Files or Share.
Convert Cat remembers your last Resize settings, so the same job next time takes only a couple of taps.
The size choices
Under Pixels, Resize offers these ready-made sizes:
- Original size: keep every pixel
- Email: 1600 px long side
- Instagram: 1080 px long side
- Full HD: 1920 px long side
- Messages & web: 1280 px long side
- Small: 800 px long side
With a long-side size, smaller photos are never enlarged. A photo that is already 1000 pixels on its long side stays that size if you pick Email.
Resize to exact pixels
When a form gives you a number, tap Custom ("Percent, long side or exact pixels"). Then choose how to set it:
- Percent: move the Scale slider from 5% to 100%, in steps of 5.
- Long side: type the number of pixels for the longer edge.
- Exact: type a Width and a Height in px. It starts at 1080 × 1080.
Tap a number to type over it, and tap Done above the keypad when you're finished. Sizes from 1 to 20,000 px are accepted.
With Exact, if your photo's shape is different from the size you typed, the photo fills the frame and the edges are trimmed evenly. Nothing is stretched. To keep the whole photo, type the width and tap Match the first photo's shape, which sets the height from your first photo's proportions. In a batch, photos of a different shape are still trimmed.
Keep the format, or change it
Resize keeps each photo's own format unless you change it, so an iPhone photo (HEIC) stays HEIC. HEIC opens on iPhone, iPad and Mac, but if the photo is going to a Windows computer, an email or a website, open More options and pick JPEG ("Opens everywhere") under Format. The Keep original format choice notes that WebP and TIFF become JPEG.
More options also has the quality slider and a Target size choice, if the file has to be under a size like 1 MB as well as a pixel size. For more on that, see how to reduce photo file size on iPhone. If all you need is a JPEG, see how to convert HEIC to JPG on iPhone.
Before you share: the hidden photo info
On the same screen, under Hidden photo info, you choose what happens to the information inside each photo: Remove location & photo info ("Recommended for sharing"), Remove location only, or Keep everything. Photos can carry where they were taken (GPS), the date, and the phone or camera, and anyone you send the file to can read it. If any of your photos has a location saved, the screen tells you how many.
Your originals stay as they are
Convert Cat works on copies. Your originals in Photos and Files aren't changed, and the result screen says "originals untouched". Save to Photos adds the resized photos as new photos. Finished files also wait in History, which keeps your last 40 conversions, so you can save or share them again later.
What it costs
Resizing is free, for as many photos as you pick: every ready-made size, custom percent, long side and exact pixels, changing the format and removing photo info. There's no watermark, no ads and no account.
Convert Cat Pro is an optional, one-time purchase (the App Store shows the price). For photo conversions it adds Saved presets, Name your files, Shortcuts and Convert from the share sheet. You don't need it to resize. More on the Convert Cat page.
Quick answers
How do I resize a photo to exact pixels on iPhone?
In Convert Cat, tap Choose Photos, then Resize, then Custom and Exact. Type the Width and Height and tap Resize.
Will resizing stretch or squash my photo?
No. With Exact, if the shape is different, the photo fills the frame and the edges are trimmed evenly. To keep the whole photo, use Match the first photo's shape or a long-side size.
Can I resize many photos at once?
Yes. Pick as many as you like, and the same size is used for each one.
Can I make a small photo bigger?
Long-side sizes never enlarge a photo, and Percent stops at 100%. Exact makes the photo the width and height you type, so a size bigger than the photo enlarges it.
Does it change my original photo?
No. Convert Cat works on copies, and your photos in Photos and Files stay as they are.
Try Convert Cat
Try Convert Cat: free, no watermark, no sign-up → iyio.com/apps/convert-cat