All JPEGs are not

the same


It’s not unusual as designers to ask our clients for a large JPEG image and to be presented with something that’s not quite big enough for what it’s needed for. You may think that all JPEGs are the same, and that we are being overly fussy, but that is not the case.

A JPEG is the most common image file format used by digital cameras and other image capturing devices. It supports 16,777,216 colours and can display more than 16 million colours at once. JPEGs come in an assortment of sizes and that’s largely down to the way they are constructed. Pictures with more colour and detail will be larger than those that are black and white and show one simple object.

JPEGs come in an assortment of sizes and that’s largely down to the way they are constructed

Rasters and pixels

It is a raster image, or bitmap image. A bitmap is a grid of individual pixels that when combined create an entire image. In other words, raster images are a collection of countless tiny squares (or pixels) of colour that are each coded in a specific hue or shade that when put together create a whole image that makes sense when you look at it.

Best sizes for online and print

So, if a JPEG is made of pixels, what sizes are the best ones to have for online or print purposes? What’s worth bearing in mind is that if an image is used too large it can become pixelated or distorted. The largest size that a JPEG supports is 65,535 x 65,535 pixels, which is huge, bearing in mind that for print we usually only require a minimum of 1000 pixels or approx. 300 dpi.

A JPEG file-size can vary for several distinct reasons:

The physical size of the file when opened/viewed

The nature of the image - how complex it is

The colour mode - RGB/CMYK/etc

Compression used - high, medium or low

Sizing guide

Bearing this in mind, we have produced a VERY rough guide for how big you would ideally need each JPEG to be (on average) for different uses:

100kb and below – probably useful as small images and thumbnails on a website

100kb to 500kb – Probably medium to large use on a website, such as a blog image or header image for a page

300kb to 1mb – likely to be ok to be printed at around A6 size, possibly A5

1mb to 2mb – likely to be ok to be printed at around A5 size, possibly A4

2mb+ likely to be fine for printing at A4

In terms of print, we recommend that you use, or provide to your designer, the largest file available, as this will give the best result. Don’t reduce it just to make it email-able, use a file transfer service. For websites you want to get the smallest file possible that doesn’t affect the quality of the image, as smaller files load quicker which is better for the user and more favoured by Google

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