I need to replace the blades on my ceiling fan?

No they aren't standard size. A bit of difference in a set of new blades is not important, but while most have three mount screws, there can be a large difference in the screw hole pattern from one manufacturer to another. Even from one model to another. Take one of the blades to a home center get the proper match. Suggestion: Replace the L brackets that support the blades as well. They are all made of cheap alloy and many times won't outlive the original blade before they start breaking.

yes you can buy replacement blades. the three holes are standard. all you need to know is the length of the overall fan. the diameter. Your local hardware store should carry them, i know Home depot does. from size 38-52. or u can just take ur old blade in and match it up.