crate documentation minimum rustc 1.15 Travis status

Big integer types for Rust, BigInt and BigUint.


Add this to your Cargo.toml:

num-bigint = "0.2"

and this to your crate root:

extern crate num_bigint;


The std crate feature is mandatory and enabled by default. If you depend on num-bigint with default-features = false, you must manually enable the std feature yourself. In the future, we hope to support #![no_std] with the alloc crate when std is not enabled.

Implementations for i128 and u128 are only available with Rust 1.26 and later. The build script automatically detects this, but you can make it mandatory by enabling the i128 crate feature.


Release notes are available in


The num-bigint crate is tested for rustc 1.15 and greater.


While num-bigint strives for good performance in pure Rust code, other crates may offer better performance with different trade-offs. The following table offers a brief comparison to a few alternatives.

CrateLicenseMin rustcImplementation
num-bigintMIT/Apache-2.01.15pure rust
rampApache-2.0nightlyrust and inline assembly
rugLGPL-3.0+1.18bundles GMP via gmp-mpfr-sys
rust-gmpMITstable?links to GMP
apintMIT/Apache-2.01.26pure rust (unfinished)