How to Fix “invalid conversion from ‘const char*’ to ‘char’” in C++

Short answer: you gave a variable a value of the wrong type, and C++ won’t convert it for you. The most common case is double quotes where you meant single quotes: "A" is text, 'A' is one character. The same family of errors covers text stored in a number, a std::string used as an int, and a pointer given a plain value instead of an address.

How to Read the Error

Every version of this error names two types: what you gave, and what the variable needed.

invalid conversion from 'const char*' to 'char'
                        ^ what you gave    ^ what it needed

const char* (or const char [2] in Clang and Visual Studio) means text in double quotes. Once you know what the two types are, the fix is usually obvious.

Cause 1: Double Quotes for a Single Character

#include <iostream>

int main() {
    char grade = "A";
    std::cout << grade << '\n';
}

GCC:    error: invalid conversion from 'const char*' to 'char' [-fpermissive]
Clang:  error: cannot initialize a variable of type 'char' with an lvalue of type 'const char[2]'
MSVC:   error C2440: 'initializing': cannot convert from 'const char [2]' to 'char'

A char holds exactly one character, written in single quotes. "A" in double quotes is a string: the letter A followed by a hidden '\0' that marks the end, which is why Clang and Visual Studio call it const char[2].

Fix: use single quotes:

#include <iostream>

int main() {
    char grade = 'A';
    std::cout << grade << '\n';
}

A

If you wanted more than one character, use std::string grade = "A+"; instead.

Cause 2: A Number in Quotes

#include <iostream>

int main() {
    int age = "21";
    std::cout << age + 1 << '\n';
}

GCC:    error: invalid conversion from 'const char*' to 'int' [-fpermissive]
Clang:  error: cannot initialize a variable of type 'int' with an lvalue of type 'const char[3]'
MSVC:   error C2440: 'initializing': cannot convert from 'const char [3]' to 'int'

"21" is the two characters 2 and 1, not the number 21. Fix: drop the quotes: int age = 21;.

Cause 3: A std::string Used as an int

Text you read from the user or a file arrives as a string, even when it looks like a number:

#include <iostream>
#include <string>

int main() {
    std::string input = "42";
    int number = input;
    std::cout << number + 1 << '\n';
}

GCC:    error: cannot convert 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'int' in initialization
Clang:  error: no viable conversion from 'std::string' (aka 'basic_string<char>') to 'int'
MSVC:   error C2440: 'initializing': cannot convert from 'std::string' to 'int'

Fix: convert it with std::stoi:

#include <iostream>
#include <string>

int main() {
    std::string input = "42";
    int number = std::stoi(input);
    std::cout << number + 1 << '\n';
}

43

If the text isn’t a number, std::stoi throws an exception, and the program stops with terminate called after throwing unless you catch it. See string to int for safer ways to handle bad input.

Cause 4: An int Used as a std::string

The other direction fails too:

#include <iostream>
#include <string>

int main() {
    int score = 95;
    std::string message = score;
    std::cout << message << '\n';
}

GCC:    error: conversion from 'int' to non-scalar type 'std::string' {aka 'std::__cxx11::basic_string<char>'} requested
Clang:  error: no viable conversion from 'int' to 'std::string' (aka 'basic_string<char>')
MSVC:   error C2440: 'initializing': cannot convert from 'int' to 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>'

Fix: use std::to_string:

#include <iostream>
#include <string>

int main() {
    int score = 95;
    std::string message = std::to_string(score);
    std::cout << message << '\n';
}

95

Watch out for this one, because it compiles without an error or a warning:

#include <iostream>
#include <string>

int main() {
    std::string message;
    message = 42;
    std::cout << message << '\n';
}

*

Assigning a number to an existing string treats it as a character code, and character 42 is *. Use std::to_string whenever you mean the digits. More in int to string.

Cause 5: char* Pointing at a String Literal

#include <iostream>

int main() {
    char* name = "Sam";
    std::cout << name << '\n';
}

GCC:    warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
Clang:  warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
MSVC:   error C2440: 'initializing': cannot convert from 'const char [4]' to 'char *'
        note: Conversion from string literal loses const qualifier (see /Zc:strictStrings)

Text in double quotes is read-only, so C++ only lets a const char* point at it. GCC and Clang compile this with a warning. Visual Studio refuses when Conformance mode (/permissive-) is on, which Microsoft’s documentation says is the default for new projects. That’s why code copied from an older tutorial can build on one setup and fail on another.

Fix: add const, or better, use std::string:

#include <iostream>

int main() {
    const char* name = "Sam";
    std::cout << name << '\n';
}

Sam

See string vs char array for when to use each.

Cause 6: A Pointer Given a Value Instead of an Address

#include <iostream>

int main() {
    int score = 90;
    int* ptr = score;
    std::cout << *ptr << '\n';
}

GCC:    error: invalid conversion from 'int' to 'int*' [-fpermissive]
Clang:  error: cannot initialize a variable of type 'int *' with an lvalue of type 'int'
MSVC:   error C2440: 'initializing': cannot convert from 'int' to 'int *'

A pointer stores an address. score is the value 90, so C++ refuses to treat it as an address.

Fix: take the address with &:

#include <iostream>

int main() {
    int score = 90;
    int* ptr = &score;
    std::cout << *ptr << '\n';
}

90

If pointers still feel slippery, see pointers in C++.

A Note on -fpermissive

GCC’s message ends with [-fpermissive], which looks like a suggestion. It isn’t a fix: that flag makes GCC accept some broken code with a warning, and the program can then behave strangely. Fix the types instead.

Quick Reference

For other common messages, see C++ error messages explained.

Take Your C++ Further

Pointers and references are where most C++ beginners get stuck, and they're far easier once you can picture them. C++ Better Explained explains them with diagrams and analogies, then builds on them to cover memory and OOP.

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Related Articles

• C++ Error Messages Explained — the most common errors and what they mean.
• How to Convert a String to an int in C++ — stoi and safer alternatives.
• How to Convert an int to a String in C++ — to_string and friends.
• Pointers in C++ — addresses, & and *, explained.
• Type Casting in C++ — when you really do need a conversion.