diff --git a/src/AstroSimBase.jl b/src/AstroSimBase.jl
index 398bde1..5b98899 100644
--- a/src/AstroSimBase.jl
+++ b/src/AstroSimBase.jl
@@ -9,6 +9,7 @@ export TimeIntegration, Euler, Leapfrog, RK4
 export BoundaryCondition, Periodic, Dirichlet, Vacuum, Newman, Reflective
 
 export traitstring, emptyfunction
+export randin
 export mkpathIfNotExist
 export need_to_interrupt, interrupt
 
@@ -97,6 +98,15 @@ function interrupt(OutputDir::String)
     close(f)
 end
 
+"""
+function randin(T, a, b)
+function randin(a, b)
+
+Generate uniform random number in `[a,b]`. It avoids error from `rand(a:b)` where `a` and `b` are `Unitful.Quantity`
+"""
+randin(T, a, b) = T(rand(T) * (b-a) + a)
+randin(a, b) = rand() * (b-a) + a
+
 include("precompile.jl")
 
 end # module AstroSimBase
\ No newline at end of file
diff --git a/test/runtests.jl b/test/runtests.jl
index 411f676..55ff2f7 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -43,4 +43,10 @@ end
     @test isfile("output/stop")
     sleep(0.2)
     @test !isfile("output/stop")
+
+    r = randin(Float32,2,3)
+    @test 2<=r<=3
+
+    r = randin(2,3)
+    @test 2<=r<=3
 end