By the indirect Archimedean method, the density and the density-temperature relationship of the Sn-40Pb eutectic alloy and two Pb-free solders, Sn-57Bi and Sn-9Zn eutectic alloys, were measured from room temperature to about 250°C. The results showed that the density-temperature dependence for each alloy in both solid and melting states can be fitted linearly as ρ S (Sn-40Pb) ϭ 8.51 Ϫ 8.94 ϫ 10 Ϫ4 (TϪ25°C), ρ L (Sn-40Pb) ϭ 8.15 Ϫ 13.8 ϫ 10 Ϫ4 (TϪT m ); ρ S (Sn-57Bi) ϭ 8.54 Ϫ 5.86 ϫ 10 Ϫ4 (TϪ25°C),ρ L (Sn-57Bi) ϭ 8.51 Ϫ 10.9 ϫ 10 Ϫ4 (TϪT m ); and ρ s (Sn9Zn) ϭ 7.22 Ϫ 7.78 ϫ 10 Ϫ4 (TϪ25°C), ρ L (Sn-9Zn) ϭ 6.89 Ϫ 5.88 ϫ10 Ϫ4 (TϪT m ), where the density unit was g/cm 3 . At the melting point, density of the melt of these solders is 8.15 g/cm 3 , 8.51 g/cm 3 , and 6.89 g/cm 3 , respectively. The density decreased 2.6% for Sn-40Pb eutectic alloy during melting, and 2.7% for Sn-9Zn eutectic alloy, but increased 0.5% for Sn-57Bi eutectic alloy. The excess molar volume for these alloys after mixing at their melting point is 0.03 cm 3 /mol for Sn-40Pb, 0.09 cm 3 /mol for Sn-57Bi, and 0.21 cm 3 /mol for Sn-9Zn.