R uses the sample version of variance, i.e. the one with denominator n - 1 instead of n. It's preferable as it gives unbiased estimate to population variance. See below:
x <- c(-8.5, 1.2, 1.5, 5.6, 2.4, 6.54, 25.21)
sum((x - mean(x)) ^ 2) / length(x)
#> [1] 89.53117
sum((x - mean(x)) ^ 2) / (length(x) - 1)
#> [1] 104.453
var(x)
#> [1] 104.453
Created on 2019-07-05 by the reprex package (v0.3.0)
Hope this helps.