小数⇔分数 変換ツール
最近接分数への変換
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Quick Answer
Convert decimals to fractions by multiplying by the desired denominator. 0.375 = 3/8 (multiply by 8, get 3). Common equivalents: 1/4 = 0.25, 1/3 = 0.333, 1/2 = 0.5, 3/4 = 0.75. Essential for drill sizes, machining, and Imperial measurements.
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Conversor de Decimal para Fracao
Converta numeros decimais em fracoes e vice-versa.
Design Notes
Fractional inches are standard in US manufacturing: drill bit sizes, wrench sizes, pipe fittings, and lumber dimensions all use fractions. PCB mounting holes typically use fractional inch drills (1/8 inch, 5/32 inch). The continued fraction algorithm finds the best rational approximation.
Common Mistakes
- 1
Confusing decimal inches with fractional inches — 0.125 inch = 1/8 inch, not approximately 1/8.
- 2
Using fractions for metric measurements — metric uses decimals (2.5 mm, not 2 1/2 mm).
- 3
Forgetting to reduce fractions to lowest terms after conversion.
Knowledge Base
なぜ小数でなく分数を使う？
製造業で必須：ドリルサイズ（1/16"）、レンチサイズ（7/16"）、配管接続（1/2"）。
小数から分数への変換方法は？
目標分母で掛ける：0.375 × 8 = 3、つまり 0.375 = 3/8。
よく使う分数-小数の対応は？
1/4=0.250、1/3=0.333、1/2=0.500、3/4=0.750、7/8=0.875。
分数の約分方法は？
分子と分母を最大公約数で割る。12/16：GCD=4 → 3/4。
機械加工の分数精度は？
一般：1/64"（0.4mm）。CNC：0.001"（25.4µm）以上、通常は小数表記。