How many megapixels do I need for a specific print size?

People often ask me questions around how many megapixels they need for a specific print size. This is a common question and it seems a source of confusion and frustration for many.

Today, most modern cameras have enough megapixels to cover all print sizes most people would want, but this question seems to keep coming up. Sometimes it's in the form of how big a print can I make with my camera? Or I want to make 8x10 inch (or A4) prints, how many megapixels do I need? Or can I print tabloid (or A3) with my camera?

The short answer is if you bought your camera in the last couple of years, don't worry. You have enough megapixels for an A3 photograph, and probably even higher.

The long answer is it depends. It's important to understand that the final quality of a print is not based purely on the megapixels of your camera. Many factors influence a final photograph, such as:

• Exposure accuracy
• Focus
• Lens quality
• Sensor dust
• Sensor size (or more accurately, pixel size)
• Ink and paper choice
• Post-processing

As an example, I have printed photographs from my very old 6 megapixel Nikon D70s at 16" x 16" that look amazing. And this is a 10 year old camera! But I have also printed photographs from the same camera at 5" x 7" that look pretty average. Megapixels definitely are not the be all, end all of print quality.

Another point to consider is viewing distance. You can expect the viewer to hold a 5x7 print and look at it up close, but you wouldn't expect them to do the same with a 40 inch one. Bigger prints are usually framed and hanging from a wall, where the viewing distance is a meter or more. Resolution is not as critical in this case. Think of a billboard up in the roof of a building. If you got close enough to it, say 30 cms (the size of a standard school ruler), you'll see the photograph is highly pixelated and blurry, but from farther away (the appropriate viewing distance), it looks fine. Consider the viewing distance when deciding on the print size and how many megapixels you might need.

All things being equal, the table below will give you an idea of the maximum print sizes you can make from a given camera's megapixels. File sizes are based on a 12 bits/pixel RAW file. Hi-Res Print are based on 300dpi, which is roughly the standard for "photo quality" prints. Normal Print sizes will give you a good print if you start with a good file to begin with.

MP	Resolution	Filesize	Hi-Res Print	Normal Print
2	1600x1200	~ 2MB	5" x 4" (13cm x 10cm)	10" x 8" (27cm x 20cm)
3	2048x1536	~ 3MB	7" x 5" (17cm x 13cm)	13" x 10" (35cm x 26cm)
5	2560x1920	~ 6MB	8" x 6" (21cm x 16 cm)	17" x 13" (43cm x 32cm)
6	2816x2112	~ 8MB	9" x 7" (24cm x 18cm)	19" x 14" (48cm x 36cm)
8	3264x2468	~ 12MB	11" x 8" (28cm x 21 cm)	21" x 16" (55cm x 42 cm)
12	4000x3000	~ 18MB	13" x 10" (34cm x 25cm)	26" x 20" (68cm x 50cm)
24	6048x4032	~36MB	20" x 13" (51cm x 34cm)	40" x 27" (100cm x 68cm)

In summary, if you have 5 megapixels (photos from your iPhone 4) you can print 8X10 with pretty decent quality (assuming a well exposed and sharp file). And if you have 10 megapixels you can print an A3 size photograph at photo quality. Most modern cameras have at least 10 megapixels.