diff --git a/convert/ft_atou.c b/convert/ft_atou.c
new file mode 100644
index 0000000..5385e94
--- /dev/null
+++ b/convert/ft_atou.c
@@ -0,0 +1,40 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   ft_atou.c                                          :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: rparodi <marvin@42.fr>                     +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2023/11/08 17:22:41 by rparodi           #+#    #+#             */
+/*   Updated: 2025/09/08 10:16:01 by rparodi          ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include <stddef.h>
+
+static int	ft_check_space(int c)
+{
+	if (c == 32 || (c >= 9 && c <= 13))
+		return (1);
+	return (0);
+}
+
+size_t	ft_atou(const char *nptr)
+{
+	size_t	i;
+	size_t	number;
+
+	if (!nptr)
+		return (0);
+	i = 0;
+	number = 0;
+	while (nptr[i])
+	{
+		if (nptr[i] >= '0' && nptr[i] <= '9')
+			number = (number * 10) + nptr[i] - '0';
+		else
+			break ;
+		i++;
+	}
+	return (number);
+}
diff --git a/includes/convert.h b/includes/convert.h
index f3dcd96..d7867c3 100644
--- a/includes/convert.h
+++ b/includes/convert.h
@@ -6,13 +6,15 @@
 /*   By: rparodi <rparodi@student.42.fr>            +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2024/10/31 14:57:24 by rparodi           #+#    #+#             */
-/*   Updated: 2025/09/05 16:07:54 by rparodi          ###   ########.fr       */
+/*   Updated: 2025/09/08 10:17:01 by rparodi          ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
 #ifndef CONVERT_H
 # define CONVERT_H
 
+# include <stddef.h>
+
 /**
  * @brief Converts integer to string
  *
@@ -29,6 +31,14 @@ char			*ft_itoa(int n);
  */
 int				ft_atoi(const char *nptr);
 
+/**
+ * @brief Converts string to size_t
+ *
+ * @param nptr the string that will be converted
+ * @return The unsigned long long on the string
+ */
+size_t	ft_atou(const char *nptr);
+
 /**
  * @brief Converts string to long long integer
  *
diff --git a/test/convert/test_atoi.c b/test/convert/test_atoi.c
index d065a80..681f7df 100644
--- a/test/convert/test_atoi.c
+++ b/test/convert/test_atoi.c
@@ -6,7 +6,7 @@
 /*   By: rparodi <rparodi@student.42.fr>            +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/09/04 16:54:42 by rparodi           #+#    #+#             */
-/*   Updated: 2025/09/05 15:05:21 by rparodi          ###   ########.fr       */
+/*   Updated: 2025/09/08 10:07:43 by rparodi          ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -19,11 +19,11 @@
 int	main(void)
 {
 	const char	*str[] = {"", "0", "42", "-42", "+-42", "-2147483648",
-		"2147483647"};
+		"2147483647", "\v\t13", "\r\n7"};
 	size_t		i;
 
 	i = 0;
-	while (i < 7)
+	while (i < 9)
 	{
 		if (ft_atoi(str[i]) != atoi(str[i]))
 		{
diff --git a/test/convert/test_atoll.c b/test/convert/test_atoll.c
index 323e6a5..a2e3764 100644
--- a/test/convert/test_atoll.c
+++ b/test/convert/test_atoll.c
@@ -6,7 +6,7 @@
 /*   By: rparodi <rparodi@student.42.fr>            +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/09/04 16:54:42 by rparodi           #+#    #+#             */
-/*   Updated: 2025/09/05 15:05:31 by rparodi          ###   ########.fr       */
+/*   Updated: 2025/09/08 10:08:15 by rparodi          ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -19,7 +19,7 @@
 int	main(void)
 {
 	const char	*str[] = {"", "0", "42", "-42", "+-42", "-2147483648",
-		"2147483647", "9223372036854775807", "-9223372036854775808"};
+		"2147483647", "\v\t13", "\r\n7"};
 	size_t		i;
 
 	i = 0;
diff --git a/test/convert/test_atou.c b/test/convert/test_atou.c
new file mode 100644
index 0000000..6f8e669
--- /dev/null
+++ b/test/convert/test_atou.c
@@ -0,0 +1,41 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   test_atou.c                                        :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: rparodi <rparodi@student.42.fr>            +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2025/09/04 16:54:42 by rparodi           #+#    #+#             */
+/*   Updated: 2025/09/08 10:20:37 by rparodi          ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "color.h"
+#include "convert.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+int	main(void)
+{
+	const char	*str[] = {"", "0", "42", "-42", "+-42",
+		"2147483647", "\v\t13", "\r\n7"};
+	size_t		i;
+	char		*end;
+
+	i = 0;
+	while (i < 9)
+	{
+		if (ft_atou(str[i]) != strtoull(str[i], &end, 10))
+		{
+			dprintf(2, "%s✘ Found %zu, expected %llu%s\n", CLR_RED,
+				ft_atou(str[i]), strtoull(str[i], &end, 10), RESET);
+			exit(1);
+		}
+		else
+			printf("%s✔%s ", CLR_GREEN, RESET);
+		i++;
+	}
+	ft_atou(NULL);
+	printf("%s✔%s", CLR_GREEN, RESET);
+	puts("\n");
+}
diff --git a/test/convert/test_itoa.c b/test/convert/test_itoa.c
index fb273fe..b84d08b 100644
--- a/test/convert/test_itoa.c
+++ b/test/convert/test_itoa.c
@@ -6,7 +6,7 @@
 /*   By: rparodi <rparodi@student.42.fr>            +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/09/04 16:54:42 by rparodi           #+#    #+#             */
-/*   Updated: 2025/09/05 16:10:48 by rparodi          ###   ########.fr       */
+/*   Updated: 2025/09/08 10:09:06 by rparodi          ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -19,7 +19,7 @@
 
 int	main(void)
 {
-	const int	integer[] = {0, 42, -42, + -42, -2147483648, 2147483647};
+	const int	integer[] = {0, 42, -42, +-42, -2147483648, 2147483647, 13, 7};
 	char		result[1024];
 	size_t		i;