Is There a Weight Limit on Mail Sent to an Inmate?

The good news is that there is no blanket weight restriction on mail sent to inmates. What matters is that the envelope has sufficient postage to cover whatever is inside. An underpaid envelope will be returned to the sender rather than delivered, so making sure the postage is right before dropping it in the mail is the one practical step worth taking.

For 12 standard 4x6 photos, a single first-class stamp will not be enough. A reasonable estimate is that a standard stamp covers roughly 6 to 7 photos at that size before the envelope crosses into additional postage territory. With 12 photos, you are likely looking at two stamps or a trip to the post office to have it weighed and stamped accurately. Erring on the side of more postage is always the safer call.