As a gallery owner the most common question I get from emerging artists (and occasionally established artists) is how to price their artwork. Working out pricing is sometimes more difficult then creating the artwork itself, but once you work out the best formula that suits you then it’s a breeze!
The best thing to do first is visit the galleries around your area, find artists that you may know are at a similar level to you (similar reputation, credentials and experience). Make sure you locate a few that are priced at a reasonable rate and take note of the size and price. 
You can work out an hourly rate that you want to pay yourself but if your artwork takes about the same amount of time per square inch then use a formula for the size instead.
To get the square inches of a painting, multiply the width of the work by the length. Next, multiply this number by a dollar amount that makes sense for your reputation and credentials. Add the cost of your materials and add it to the square inch dollar amount. If you’re paying a commission add that to the material cost instead of the artwork. Then round it up to a clean amount.
For a 12 x 12 inch (30.5 x 30.5cm) painting
Price per square inch: 12 x 12 = 144 sqr inches, 144 sqr inches x $1.5 = $216. 
Add materials (eg $10) and the galleries commission on materials (+ 30% $13) = $23.
$216 + $23 = $239. 
Round up to $240.
NB: this is using a $1.5 sqr inch formula. You can use a higher amount according to your reputation, credentials and experience.
The most common practice is to price per square inch but if you have a large variety of sizes (very small and very large) then you may need to use the linear formula instead.
For a 12 x 12 inch (30.5 x 30.5cm) painting
Using linear inches: 12 + 12 = 24 linear inches, 24 linear inches × $10 = $240. 
Your linear formula should include an average priced frame (and materials) and an average commission.
NB: this is using a $10 amount which includes an average priced frame and materials and with an average 30% commission. You can use a higher amount according to your reputation and experience.
Here is an example of why linear inches works well if you do a large variety of sizes. When you use per square inch the formula ends up pricing your huge pieces a little to high!
For example, if you are using per square inch formula: 12 x 12 inch = $216 but a 48 x 48 inch = $3456.
Plus you still need to add commission and materials.
If you are using linear inches: 12 x 12 inch = $240 but a 48 x 48 inch = $960
Pricing your work consistently allows you to build credibility and establish an excellent reputation amongst buyers and collectors. Buyers like to understand how art is priced. It will also keep you in your galleries good books!  You’ve had fun in the studio but now it’s time to put your business hat on!
NB: I have used inches due to most canvases are labeled this way. 1 inch = 2.5cm.
If you need any further assistance with pricing then please pop in to The Space – Gallery + Workshops.
I’m always happy to help.