# Solidity concatenate uint into a string?

How would I concatenate an integer into a string using solidity?

For instance, say I have the following:

``````uint myInteger = 12
``````

How can I create the following string `"My integer is: 12"` with 12 being the value of myInteger.

In other words have, `"My integer is: " + myInteger`

Try the following:

``````pragma solidity ^0.4.4;

contract TestIntToString {

string public result;

function TestIntToString() {
// result = uintToString(12345678901234567890);
result = appendUintToString("My integer is: ", 1234567890);
}

function uintToString(uint v) constant returns (string str) {
uint maxlength = 100;
bytes memory reversed = new bytes(maxlength);
uint i = 0;
while (v != 0) {
uint remainder = v % 10;
v = v / 10;
reversed[i++] = byte(48 + remainder);
}
bytes memory s = new bytes(i);
for (uint j = 0; j < i; j++) {
s[j] = reversed[i - 1 - j];
}
str = string(s);
}

function appendUintToString(string inStr, uint v) constant returns (string str) {
uint maxlength = 100;
bytes memory reversed = new bytes(maxlength);
uint i = 0;
while (v != 0) {
uint remainder = v % 10;
v = v / 10;
reversed[i++] = byte(48 + remainder);
}
bytes memory inStrb = bytes(inStr);
bytes memory s = new bytes(inStrb.length + i);
uint j;
for (j = 0; j < inStrb.length; j++) {
s[j] = inStrb[j];
}
for (j = 0; j < i; j++) {
s[j + inStrb.length] = reversed[i - 1 - j];
}
str = string(s);
}
}
``````

Here is the Browser Solidity screen showing the workings of this algorithm:

• Is there a reason maxlength is 100 and not 78? The maximum number of digits possible with uint256 is 78. Commented Mar 13, 2018 at 17:02
• Doesn't work anymore.Remix throws an error saying `explicit conversion from uint256 to bytes1 is unsupported` for the line `reversed[i++] = byte(48 + remainder)` Commented Sep 8, 2019 at 13:08
• for conversion issue, use `byte(uint8(48 + remainder))` Commented Jun 4, 2021 at 10:22
• This code is not working because type mismatch ****reversed[i++] = byte(48 + remainder)**** Commented Mar 30, 2023 at 3:56

This is my first answer here :)

1. You can use openzeppelin's Strings.sol, and use toString(value) method to convert a number to a string.

toString(value): Converts a uint256 to its ASCII string decimal representation.

1. Now to concat, we can use string.concat() [available after solidity version 0.8.12].

it'll look like this:

``````pragma solidity ^0.8.12;
import "@openzeppelin/contracts/utils/Strings.sol";

contract NumToStr {

function testConcat(uint256 num1) public pure returns (string memory) {
return string.concat("The number is: ",Strings.toString(num1), ", Cool!!");
}
}
``````

there are other methods in openzeppelin's Strings.sol like:

``````toHexString(value)

toHexString(value, length)

``````
• You can read more about the Strings library in openzeppelin's docs here:

• Instead of string.concat() we can also use abi.encodePacked(str1, str2), which returns bytes (see here). Then we can typecast the bytes to string with string(bytesVal):

``````function testConcat(uint256 num1) public pure returns (string memory) {
return string(abi.encodePacked("The number is: ",Strings.toString(num1), ", Cool!!"));
}
``````

But, I know this approach is kinda hacky.

• I have tried your approach (which I think is the simplest one) but for some reason is throwing me the following error: "TypeError: Type bytes memory is not implicitly convertible to expected type string memory." I'm using the Solidity compiler v8.9 Commented Dec 15, 2022 at 16:20
``````function strConcat(string _a, string _b, string _c, string _d, string _e) internal returns (string){
bytes memory _ba = bytes(_a);
bytes memory _bb = bytes(_b);
bytes memory _bc = bytes(_c);
bytes memory _bd = bytes(_d);
bytes memory _be = bytes(_e);
string memory abcde = new string(_ba.length + _bb.length + _bc.length + _bd.length + _be.length);
bytes memory babcde = bytes(abcde);
uint k = 0;
for (uint i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
for (i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
for (i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
for (i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
for (i = 0; i < _be.length; i++) babcde[k++] = _be[i];
return string(babcde);
}

function strConcat(string _a, string _b, string _c, string _d) internal returns (string) {
return strConcat(_a, _b, _c, _d, "");
}

function strConcat(string _a, string _b, string _c) internal returns (string) {
return strConcat(_a, _b, _c, "", "");
}

function strConcat(string _a, string _b) internal returns (string) {
return strConcat(_a, _b, "", "", "");
}
``````
• I don't think this answer addresses how to convert integer to a string Commented Dec 23, 2016 at 20:12
• Isn't this just a copy of the answer from the suggested duplicate thread? In which case you should also flag the question as a duplicate. Commented Dec 24, 2016 at 9:01