diff --git a/tools/clean-repos/main.go b/tools/clean-repos/main.go
index 6739191..5240340 100644
--- a/tools/clean-repos/main.go
+++ b/tools/clean-repos/main.go
@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"path/filepath"
 	"time"
 )
 
@@ -24,16 +25,41 @@ func main() {
 				log.Fatal(err)
 			}
 			for _, d := range dirs {
+				path := "_repos/src/" + f.Name() + "/" + d.Name()
 				if time.Now().Sub(d.ModTime()) > 30*24*time.Hour {
-					path := "_repos/src/" + f.Name() + "/" + d.Name()
 					if *real {
-						log.Printf("Deleting %s...", path)
+						log.Printf("Deleting %s (repo is old)...", path)
+						os.RemoveAll(path)
+						continue
+					} else {
+						log.Printf("Would delete %s (repo is old)", path)
+					}
+				}
+
+				size, err := DirSize(path)
+				if err != nil {
+					log.Fatal(err)
+				}
+				if size < 15*1000*1000 {
+					if *real {
+						log.Printf("Deleting %s (repo size < 15M)...", path)
 						os.RemoveAll(path)
 					} else {
-						log.Printf("Would delete %s", path)
+						log.Printf("Would delete %s (repo size < 15M)", path)
 					}
 				}
 			}
 		}
 	}
 }
+
+func DirSize(path string) (int64, error) {
+	var size int64
+	err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
+		if !info.IsDir() {
+			size += info.Size()
+		}
+		return err
+	})
+	return size, err
+}