Subnormal Numbers and Underflow

Updated 15 Sep 2026

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What it is
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  numbers too small to be represented in the normal $(1+m) \times 2^{e-\text{bias}}$ form (with an implicit leading 1); represented instead with an implicit leading 0 once the exponent field hits its minimum value
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Thresholds (single precision)
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  smallest normalized positive number: $1.0 \times 2^{-126} \approx 1.175 \times 10^{-38}$
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  smallest subnormal positive number: $2^{-149} \approx 1.401 \times 10^{-45}$
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  anything smaller than the subnormal minimum flushes to zero (underflow)
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Related
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  IEEE 754 Floating-Point Standard

What it is