Lime requirements ordinarily are based on buffer methods but could be based on unbuffered salt‐exchangeable acidity. The relationships between exchangeable acidity (EA) and buffer acidity (BA) were studied across a range of pH levels established through lime trials in four Ultisols and one Histisol in North Carolina Coastal Plain and Piedmont regions. Buffer acidity was proportionately higher than EA in all soils at any pH level. Linear regression slopes between either BA or EA and pH, within each soil, were not significantly different when the latter relationship included samples with pH less than or equal to 5.4. Variations in EA accounted for by BA ranged from 41 to 67% among the soils investigated. Buffer acidity alone accounted for 64% of the variation in EA for samples from all soils with pH less than or equal to 5.4. Including a squared BA term and either HM or CEC increased the R2to 0.79 and 0.86, respectively, but neither equation provided a completely suitable prediction of EA across all five soils investigated.