#format #convert #bytes #duration #throughput


Generate beautiful human representations of bytes, durations and even throughputs!

15 releases (8 breaking)

Uses new Rust 2021

new 0.9.0 Jun 22, 2022
0.7.0 Jun 9, 2022

#17 in Value formatting

Download history 293/week @ 2022-05-30 82/week @ 2022-06-06 59/week @ 2022-06-13 40/week @ 2022-06-20

474 downloads per month
Used in refine

MIT license

371 lines


Generate beautiful human representations of bytes, durations and even throughputs!

License: MIT Crates.io Docs

What it does

Easily generate several kinds of human-readable descriptions, directly on primitive numbers:

use human_repr::HumanRepr;

// counts (bytes or any other unit)
assert_eq!("43.2 MB", 43214321_u32.human_count_bytes());
assert_eq!("123.5 kPackets", 123456_u64.human_count("Packets"));

// primitive durations
assert_eq!("15.6 µs", 0.0000156.human_duration());
assert_eq!("10 ms", 0.01.human_duration());
assert_eq!("3.44 s", 3.435999.human_duration());
assert_eq!("19:20.4", 1160.36.human_duration());
assert_eq!("1:14:48", 4488.395.human_duration());

// throughputs (bytes or any other unit)
// the divisions below are just for the sake of clarity, they show 
// the very concept of a "throughput": number of items per time.
assert_eq!("1.2 MB/s", (1234567. / 1.).human_throughput_bytes());
assert_eq!("6.1 tests/m", (8. / 79.).human_throughput("tests"));
assert_eq!("9 errors/d", (125. / 1200000.).human_throughput("errors"));

And even on Duration instances:

use human_repr::HumanReprDuration;
use std::time::Duration;

assert_eq!("15.6 µs", Duration::new(0, 15_600).human_duration());
assert_eq!("10 ms", Duration::from_secs_f64(0.01).human_duration());
assert_eq!("1:14:48", Duration::new(4488, 395_000_000).human_duration());

This lib implements a whole suite of:

  • counts, supporting SI prefixes k, M, G, T, P, E, Z, and Y (optional IEC and "mixed" ones, see Rust features);
  • durations, supporting nanos (ns), millis (ms), micros (µs), seconds (s), minutes (M:SS), and even hours (H:MM:SS);
  • throughputs, supporting per day (/d), per hour (/h), per minute (/m), and per second (/s).

This crate doesn't have any dependencies, is well-tested, and is blazingly fast, taking only ~50 ns to generate a representation! (criterion benchmarks inside)
Since version 0.4, it does not even allocate any Strings! I've returned structs that implement Display, so you can print them with no heap allocations at all! And if you do need the String, a simple .to_string() will do.

They work on all Rust primitive number types: u8, u16, u32, u64, u128, usize, f32, f64, i8, i16, i32, i64, i128, isize.
Since version 0.7, Duration is also supported! Yes yes, I know it does have a Debug impl that does almost this, but it is not very human: Duration::new(0, 14184293) comes out as 14.184293ms, this crate would return 14.2 ms. And of course, the minutes and hours views... Duration::new(10000, 1) gives the horrendous 10000.000000001s, instead of 2:46:40 👍

The unit parameter some methods refer to means the entity you're dealing with, like bytes, actions, iterations, errors, whatever! Just send that text, and you're good to go!
Bytes have dedicated methods for convenience.

How to use it

Add this dependency to your Cargo.toml file:

human-repr = "0"

Then just use the main trait and that's it! You can now call on any number:

use human_repr::HumanRepr;




For durations, use the specific trait:

use human_repr::HumanReprDuration;


Rust features:

According to the SI standard, there are 1000 bytes in a kilobyte.
There is another standard called IEC that has 1024 bytes in a kibibyte, but this is only useful when measuring things that are naturally a power of two, e.g. a stick of RAM.

Be careful to not render IEC quantities with SI scaling, which would be incorrect. But I still support it, if you really want to ;)

By default, human-repr will use SI, 1000 divisor, and space between values and scales/units. SI uses prefixes: k, M, G, T, P, E, Z, and Y.

This crate supports these optional features:

  • iec => use IEC instead of SI: Ki, Mi, Gi, Ti, Pi, Ei, Zi, Yi (implies 1024);
  • 1024 => use 1024 divisor — if iec is not enabled, use prefixes: K, M, G, T, P, E, Z, and Y (note the upper 'K');
  • space [default] => include a space between values and scales/units everywhere: 48 B instead of 48B, 15.6 µs instead of 15.6µs, and 12.4 kB/s instead of 12.4kB/s.

The human duration magic

I've used just one key concept in designing the human duration features: cleanliness.

3.44 s is more meaningful than 3.43584783784 s, and 14.1 µs is much, much nicer than .0000141233333 s.

So what I do is: round values to at most two decimal places (larger scales have more decimals), and find the best scale to represent them, minimizing resulting values smaller than 1. The search for the best scale considers even the rounding been applied!

0.000999999 does not end up as 999.9 µs (truncate) nor 1000 µs (bad scale), it is auto-upgraded to the next one 1 ms!

The human duration scale changes seamlessly from nanoseconds to hours!

  • values smaller than 60 seconds are always rendered as D.D[D] scale, with one or two decimals;
  • .0 and .00 are efficiently not generated instead of removed from the output -> it is handled directly in the format arguments;
  • from 1 minute onward it changes to "M:SS";
  • from 1 hour onward it changes to "H:MM:SS".

The human throughput magic

I've made the human throughput with a similar logic. It is funny how much trickier "throughput" is to the human brain!

If something took 1165263 seconds to handle 123 items, how fast did it go? It's not obvious...

It doesn't help much even if we divide the duration by the number of items: 9473 seconds/item still does not seem that good. How fast was that? We can't say for sure.
Humm, how many items did we do per time?

Oh, we just need to invert it, so 0.000105555569858 items/second, there it is! 😂

To make some sense of it we now need to multiply that by 3600 (seconds in an hour) to get 0.38 per hour, which is much better, and again by 24 (hours in a day) to finally get 9.12 per day!! Now we know how fast that process was! \o/
As you see, it's not easy at all for our brains to estimate that...

The human throughput scale changes seamlessly from per second to per day!

  • .0 and .00 are efficiently not generated too, much like the duration magic;
  • it also automatically inserts SI prefixes when in the fastest scale (per second), so we get 2.4 MB/s or 6.42 Gitems/s 👍

The human count magic

Oh, this is the simplest of them all! I just continually divide by the divisor (1000 or 1024), until the value gets smaller than it. No funny business like logs or exponentials at all.

Rounding is also handled so there's no truncation or bad scale, the number of decimals also increase the larger the scale gets, and .0 and .00 are also never generated.

Changelog highlights

  • 0.9.x Jun 22, 2022: do not use captured identifiers in format strings, to support much broader Rust versions instead of only >= 1.58
  • 0.8.x Jun 12, 2022: change nospace feature to space, to avoid the negative logic (it is now default, to maintain behavior)
  • 0.7.x Jun 04, 2022: support for std::time::Duration via a new trait HumanReprDuration, include one decimal in the minutes representation
  • 0.6.x Jun 04, 2022: improve signed support with new ops::Neg impl
  • 0.5.x Jun 03, 2022: new minutes representation M:SS, between seconds and complete H:MM:SS
  • 0.4.x Jun 03, 2022: even faster implementation, which does not do any String allocations
  • 0.3.x Jun 01, 2022: support for a new group of prefixes for 1024 only (without iec)
  • 0.2.x Jun 01, 2022: more flexible API (impl AsRef<str>), greatly improved documentation
  • 0.1.x Jun 01, 2022: first release, include readme, method and module docs, describe features already implemented


This software is licensed under the MIT License. See the LICENSE file in the top distribution directory for the full license text.

Maintaining an open source project is hard and time-consuming, and I've put much ❤️ and effort into this.

If you've appreciated my work, you can back me up with a donation! Thank you 😊

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