diff --git a/src/lib.rs b/src/lib.rs
index 16bf1bc..b568c4e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,7 @@ use number_prefix::NumberPrefix;
 use walkdir::WalkDir;
 
 use std::{
+    collections::BTreeMap,
     fmt::Display,
     path::{Path, PathBuf},
 };
@@ -91,3 +92,95 @@ pub fn format_size(size: u64, binary: bool) -> String {
         NumberPrefix::Prefixed(prefix, number) => format!("{:.2} {}B", number, prefix),
     }
 }
+
+/// Calculate the sum of sizes of all entries
+///
+/// Does not account twice the size of entries that are within other entries.
+/// Implementation uses BTreeMap to build a path Trie.
+pub fn calculate_unique_total_size(entries: &[Entry]) -> u64 {
+    let mut filtered_entries = Vec::<&Entry>::new();
+    let mut canonicalized_paths = Vec::<PathBuf>::new();
+
+    // Canonicalize each path, silently ignoring failures.
+    // TODO: Review if we should ignore failures.
+    for entry in entries {
+        if let Ok(path) = entry.path.canonicalize() {
+            filtered_entries.push(entry);
+            canonicalized_paths.push(path);
+        }
+    }
+
+    #[derive(PartialEq, Eq, PartialOrd, Ord)]
+    struct TriePathNode {
+        // Children nodes of this current path, accessed by path.
+        children: BTreeMap<PathBuf, TriePathNode>,
+        // Size of the file that ends at this node.
+        node_size: u64,
+    }
+
+    let mut trie_root = TriePathNode {
+        children: BTreeMap::new(),
+        node_size: 0,
+    };
+
+    // For each entry/path, add it to the Trie if it wasn't already inserted.
+    //
+    // If the Trie receives a folder that is parent of a previously added file, then just consider
+    // the parent folder, removing the childs, this way, we do not count them twice towards the
+    // final total.
+    for (i, entry) in filtered_entries.iter().enumerate() {
+        let path = &canonicalized_paths[i];
+
+        // Necessary because we need to check when it's the last path piece.
+        let mut path_iter = path.iter().peekable();
+        // Pointer to traverse the tree.
+        let mut current_trie_node = &mut trie_root;
+        // Size to be added at the endif the current entry isn't children of any other.
+        let size_of_current_file = entry.size;
+
+        while let Some(piece) = path_iter.next() {
+            // Query for the node in the Trie which matches the current path piece.
+            let entry = current_trie_node.children.entry(PathBuf::from(piece));
+
+            // Keeps track if the current entry is child of another previously found.
+            let mut already_considered = false;
+            let next_trie_node = entry
+                .and_modify(|_| {
+                    // If we are in this block, it means that the node size was already considered
+                    // because a parent of it was inserted. So we will skip this file.
+                    already_considered = true;
+                })
+                // Add a node with 0 size, which may be changed after if it is the last piece.
+                .or_insert(TriePathNode {
+                    children: BTreeMap::new(),
+                    node_size: 0,
+                });
+
+            // Skipping already accounted file, because it is nested inside of another one.
+            if already_considered {
+                break;
+            }
+
+            // If we are at the last piece of the current entry path, it means that this is the tip
+            // that finally represents the file, and which path is the full file path.
+            let is_the_last_piece = path_iter.peek().is_none();
+            if is_the_last_piece {
+                // Update the size of this piece.
+                next_trie_node.node_size = size_of_current_file;
+                // Drop all the childrens so that their sizes won't be added.
+                next_trie_node.children.clear();
+            }
+
+            // Update the pointer to keep traversing the trie.
+            current_trie_node = next_trie_node;
+        }
+    }
+
+    fn trie_recursive_sum(node: &TriePathNode) -> u64 {
+        let children_sum: u64 = node.children.values().map(trie_recursive_sum).sum();
+        node.node_size + children_sum
+    }
+
+    // Traverse the trie tree to calculate the sum
+    trie_recursive_sum(&trie_root)
+}
diff --git a/src/main.rs b/src/main.rs
index b5ebd82..a58c9cb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,7 +4,7 @@ use wild;
 
 mod cli;
 use cli::Cli;
-use durt::{format_size, Entry};
+use durt::{calculate_unique_total_size, format_size, Entry};
 
 fn main() {
     #[cfg(windows)]
@@ -60,7 +60,7 @@ fn main() {
         Table::new("  {:>}  {:<}")
     };
 
-    let total_size = entries.iter().map(|e| e.size).sum();
+    let total_size = calculate_unique_total_size(&entries);
     let mut omitted_entries = 0;
 
     for entry in entries {