[ruby-core:125571] [Ruby Bug#22079] Float#ceil gives incorrect result

23 May 2026


      Issue #22079 has been updated by nobu (Nobuyoshi Nakada).

Backport changed from 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN to 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED

[GH-17097](https://github.com/ruby/ruby/pull/17097)

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Bug #22079: Float#ceil gives incorrect result
https://bugs.ruby-lang.org/issues/22079#change-117400

* Author: cryptogopher (crypto gopher)
* Status: Open
* ruby -v: ruby 3.3.7 (2025-01-15 revision be31f993d7) [x86_64-linux]
* Backport: 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED
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Let's take following number as an example:
``` ruby
...
Float::MIN
=> 2.2250738585072014e-308
This gives proper result:
```ruby
> Float::MIN.ceil(308)
=> 2.9999999999999997e-308

But this does not:
```ruby
...
Float::MIN.floor(309)
=> NaN
even though the result is perfectly valid `Float` number:
```ruby
> "2.3e-308".to_f
=> 2.3e-308

-- 
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