このガイドは英語で提供されています。
Count significant figures, round to a target precision, or apply precision rules to two-number arithmetic. Target rounding accepts 1–15 figures and shows both ordinary decimal form and scientific notation with trailing zeros preserved. Use the rounding calculator for a fixed number of decimal places.
Check significant digits in a written measurement, round to three or another number of figures, or check arithmetic precision. Measurement uncertainty and full expressions are outside the model.
Keep the original spelling: 1.200 and 1.2 have the same value but different significant counts. Use dot decimals or e scientific notation with optional signs. The mantissa allows at most 100 digits, the exponent −100 to 100 and total input 120 characters. Non-finite values and nonzero inputs that underflow to zero are rejected. Thousands separators and comma decimals are unsupported.
Target precision must be a whole number from 1 to 15. Arithmetic also needs the second number and an operator; a divisor cannot be zero. Editing clears the old result. Calculating preserves URL parameters; existing count and operation shared links still restore.
Leading zeros do not count; interior zeros do. A written decimal point preserves trailing zeros. Plain integers without a decimal point do not count trailing zeros. Scientific mantissas count explicitly written digits: 1200 has 2, 1200. has 4, 1.200e3 has 4 and 1200e3 also counts the four explicit mantissa digits.
Target rounding parses decimal strings directly, keeps the first N significant digits and increments when the next digit is at least 5. Midpoints round away from zero. A carry updates the exponent. Scientific notation keeps exactly N figures without converting back to a number and losing zeros.
乗除算と指定丸めは有効数字の精度に従います。科学的記数法では意味のある末尾の零を保ちます。
有効数字は数全体の意味のある桁を、小数点以下の桁数は小数点の後の桁を数えます。
このページでは零の桁数を 1 桁と記載した小数の零の数の合計とします。0.00 は 3 桁です。零を 3 桁に丸めると 0.00 と 0.00e+0 です。
有効数字を数え、1～15 桁に丸めて末尾の零を保った科学的記数法を表示し、二数の精度付き演算も行います。