Bare copper wire is available in 14, 16, 18 & 20 gauge, and comes in a 4 oz. spool

14 gauge, .064" (1.6mm), 4 oz. (113g), 20' (6m).
16 gauge, .051" (1.3mm), 4 oz. (113g), 32' (9.8m).
18 gauge, .04" (1.0mm), 4 oz. (113g), 50' (15.2m).
20 gauge, .032" (.8mm), 4 oz. (113g), 79' (24m).