Scale & Paisley Heart Pattern

Something I always struggle with once I've drawn up my idea, scanned it and started to repeat it, is what scale should it be?  For me, I usually end up printing it out just to confirm that I've got it at the scale I want - it's so easy to get it wrong just using your screen as a measurement.  I'm lucky to have a bigger screen to work on as some of my designs are full scale king size duvet designs.  I think it helped my last client as she was judging pattern size and lettering on her screen until I suggested doing a print out at home on her printer and it worked.  This play with scale is a heart shaped floral pattern I created as part of a paisley set for some new zazzle products.