diff --git a/src/osgb.rs b/src/osgb.rs
index 86f763e..63edc98 100644
--- a/src/osgb.rs
+++ b/src/osgb.rs
@@ -1,5 +1,6 @@
 use crate::constants::_500KM;
 use crate::grid::{coords_to_square, square_to_coords};
+use crate::utils::trim_string;
 use crate::{coordinates::point::Point as GridPoint, Error, Precision};
 use geo_types::{LineString, Point, Polygon};
 use std::fmt::Display;
@@ -27,7 +28,7 @@ pub struct OSGB {
 impl OSGB {
     /// Creates a new grid reference from the given coordinates
     /// and precision.
-    /// 
+    ///
     /// # Errors
     /// Returns an error if the given coordinates are out of bounds.
     ///
@@ -251,11 +252,7 @@ impl FromStr for OSGB {
     type Err = Error;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let string: String = s
-            .to_uppercase()
-            .chars()
-            .filter(|c| !c.is_whitespace())
-            .collect();
+        let string: String = trim_string(s);
 
         match string.chars().next() {
             Some(c) => {
diff --git a/src/osi.rs b/src/osi.rs
index 7ceb0e7..c5b0e9b 100644
--- a/src/osi.rs
+++ b/src/osi.rs
@@ -1,3 +1,4 @@
+use crate::utils::trim_string;
 use crate::{coordinates::point::Point as GridPoint, Error, Precision};
 use geo_types::{LineString, Point, Polygon};
 use std::fmt::Display;
@@ -18,7 +19,7 @@ pub struct OSI {
 impl OSI {
     /// Creates a new grid reference from the given coordinates
     /// and precision.
-    /// 
+    ///
     /// # Errors
     /// Returns an error if the given coordinates are out of bounds.
     ///
@@ -208,11 +209,7 @@ impl FromStr for OSI {
     type Err = Error;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let string: String = s
-            .to_uppercase()
-            .chars()
-            .filter(|c| !c.is_whitespace())
-            .collect();
+        let string: String = trim_string(s);
         let point: GridPoint = string.parse()?;
 
         Ok(Self { point })
diff --git a/src/utils.rs b/src/utils.rs
index f1c489e..0d2303d 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -48,9 +48,22 @@ pub fn digits(s: &str) -> Result<(u32, u32, Precision), Error> {
     ))
 }
 
+/// Removes all non-alphanumeric characters from string
+/// and converts to uppercase for parsing.
+pub fn trim_string(s: &str) -> String {
+    s.chars()
+        .filter(|c| !c.is_ascii_whitespace())
+        .map(|c| c.to_ascii_uppercase())
+        .collect()
+}
+
 #[cfg(test)]
 mod test {
-    use crate::{constants::*, utils::digits, Error, Precision};
+    use crate::{
+        constants::*,
+        utils::{digits, trim_string},
+        Error, Precision,
+    };
 
     #[test]
     fn parse_valid_digits() {
@@ -81,4 +94,11 @@ mod test {
             ))
         )
     }
+
+    #[test]
+    fn trim_strings() {
+        assert_eq!(trim_string("so 14 5"), "SO145");
+        assert_eq!(trim_string("So 222"), "SO222");
+        assert_eq!(trim_string(" @ @ "), "@@");
+    }
 }