diff --git a/README.md b/README.md
index 8d97cf09..056382a9 100644
--- a/README.md
+++ b/README.md
@@ -56,7 +56,7 @@ React is nice, Webpack is convenient, but there's just very little need to serve
 - [x] inflections
 - [x] canonical
 - [x] yforx
-- [ ] arclength
+- [x] arclength
 - [ ] arclengthapprox
 - [ ] curvature
 - [ ] tracing