Number Converter

Binary to Decimal Converter

Enter a base-2 whole number to convert it into an exact decimal integer, hexadecimal cross-check, and significant binary bit length using BigInt precision.

Convert binary to decimal

Binary to decimal formula

Decimal value = Σ(bit × 2^position), counting positions from 0 at the rightmost binary digit.

Exact large integers

Uses BigInt instead of floating-point Number conversion.

Flexible input

Accepts 0b, negative sign, spaces and underscore grouping.

Cross-check output

Shows decimal, hexadecimal and significant bit length.

How to convert binary numbers to decimal

Binary is a base-2 number system that uses only 0 and 1. Each position represents a power of two. Starting at the right, the place values are 1, 2, 4, 8, 16 and so on. Multiply each bit by its place value and add the results. For example, 101101 equals 32 + 8 + 4 + 1, which is 45 in decimal.

This converter accepts an optional 0b prefix, a leading minus sign, and spaces or underscores used for visual grouping. It removes grouping characters, validates every remaining digit, and uses BigInt so integers larger than JavaScript’s ordinary safe-number range remain exact.

Leading zeros do not change the numeric value. The significant bit count removes redundant leading zeros but still reports one bit for zero. Negative results use a minus sign rather than interpreting the input as two’s complement, because two’s complement requires a fixed bit width such as 8, 16, 32 or 64 bits.

Binary place-value examples

InputWhat it meansPlanning note
11 in decimalThe rightmost place is 2^0.
101010 in decimal8 + 2 = 10.
11111111255 in decimalEight 1 bits represent 2^8 - 1.
100000000256 in decimalA 1 followed by eight zeros is 2^8.

Common use cases

Computer science

Check exercises involving base-2 place values and bit patterns.

Programming

Interpret binary literals, flags and integer representations.

Digital systems

Translate register or logic values into familiar decimal numbers.

Frequently asked questions

How do I convert binary to decimal manually?

Multiply each bit by the corresponding power of two and add the nonzero place values.

Can I include spaces in the binary number?

Yes. Spaces and underscores are removed before validation and conversion.

Does this support very large binary integers?

Yes. The browser BigInt type preserves exact whole-number values beyond the normal safe integer limit.

Does a negative binary input use two’s complement?

No. A leading minus sign represents a negative integer directly. Two’s complement needs a specified bit width.

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Last reviewed: August 15, 2026. Integer conversions use browser BigInt for exact whole-number results.

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