TypeError: can't convert BigInt to number

The JavaScript exception "can't convert BigInt to number" occurs when an arithmetic operation involves a mix of {{jsxref("BigInt")}} and {{jsxref("Number")}} values.

Message#

TypeError: Cannot convert a BigInt value to a number (V8-based)
TypeError: Cannot mix BigInt and other types, use explicit conversions (V8-based)
TypeError: BigInts have no unsigned right shift, use >> instead (V8-based)
TypeError: can't convert BigInt to number (Firefox)
TypeError: Conversion from 'BigInt' to 'number' is not allowed. (Safari)
TypeError: Invalid mix of BigInt and other type in addition/multiplication/…. (Safari)
TypeError: BigInt does not support >>> operator (Safari)

Error type#

{{jsxref("TypeError")}}.

What went wrong?#

The two sides of an arithmetic operator must both be BigInts or both not. If an operation involves a mix of BigInts and numbers, it's ambiguous whether the result should be a BigInt or number, since there may be loss of precision in both cases.

The error also happens when a BigInt is implicitly converted to a number via the number coercion process. For example, if a BigInt is passed to a built-in method that expects a number.

The error can also happen if the unsigned right shift operator (>>>) is used between two BigInts. In Firefox, the message is the same: "can't convert BigInt to number".

Examples#

Mixing numbers and BigInts in operations#

```js example-bad const sum = 1n + 1; // TypeError: can't convert BigInt to number

Instead, explicitly coerce one side to a BigInt or number.

```js example-good
const sum = 1n + BigInt(1);
const sum2 = Number(1n) + 1;

Using unsigned right shift on BigInts#

```js example-bad const a = 4n >>> 2n; // TypeError: can't convert BigInt to number

Use normal right shift instead.

```js example-good
const a = 4n >> 2n;

See also#

• BigInt