🔬 有效数字计算器（修约 / 计数）Significant Figures Calculator (round & count)

使用说明与常见问题How-to & FAQ

「有效数字计算器（修约 / 计数）」是什么？What is the Significant Figures Calculator (round & count) tool?

按指定有效数字位数修约（按输入的十进制数字四舍五入，9.995 → 10.0 / 1.00×10¹），或数一个数有几位有效数字（含科学计数法，并指出整数末尾 0 的歧义）。本地处理。Round to N significant figures (half-up on the decimal digits you type: 9.995 → 10.0 / 1.00×10¹), or count the significant figures in a number (scientific notation supported; ambiguous trailing zeros in whole numbers are flagged). Processed locally.

如何使用「有效数字计算器（修约 / 计数）」？How do I use the Significant Figures Calculator (round & count) tool?

在「有效数字计算器（修约 / 计数）」中，填写「模式」、「数值」、「有效数字位数」等参数，结果会随输入实时计算并显示在下方。In the Significant Figures Calculator (round & count): Fill in "Mode", "Number", "Significant figures"; results are recalculated instantly as you type.

修约用什么规则？Which rounding rule is used?

四舍五入（第 N+1 位是 5 或以上就进位），并且直接按你输入的十进制数字计算，避免 9.995 这类数在二进制浮点里变成 9.99499… 而被舍掉。部分教材用“四舍六入五成双”，结果可能在恰好为 5 时不同。Round half up (if the next digit is 5 or more, round up), applied directly to the decimal digits you type, so numbers like 9.995 are not turned into 9.99499… by binary floating point. Some textbooks use round-half-to-even, which can differ when the dropped part is exactly 5.

1200 有几位有效数字？How many significant figures does 1200 have?

有歧义：2 到 4 位。末尾的 0 可能只是占位。写成 1200.（带小数点）是 4 位，写成 1.2×10³ 是 2 位，1.20×10³ 是 3 位。It is ambiguous: 2 to 4. The trailing zeros might be placeholders. 1200. (with a point) has 4, 1.2×10³ has 2 and 1.20×10³ has 3.

可以输入科学计数法吗？Can I type scientific notation?

可以：1.20e3、1.20E3、1.20×10^3 都行；计数时只看系数 1.20（3 位）。Yes: 1.20e3, 1.20E3 or 1.20×10^3; when counting, only the coefficient 1.20 matters (3 figures).

能举个计算实例吗？Can you show a worked example?

例如在「有效数字计算器（修约 / 计数）」中填 模式 = 修约到 N 位有效数字，数值 = 1234.56，有效数字位数 = 3，结果区显示：结果：1230；科学计数：1.23×10³；E 记法：1.23e+3；⚠ 普通写法 1230 末尾的 0 看不出是否有效，请用科学计数法 1.23×10³ 表示 3 位有效数字；ℹ 按你输入的十进制数字四舍五入（5 进位），不经过二进制浮点，所以 9.995 修约 3 位是 10.0For example, entering Mode = Round to N significant figures, Number = 1234.56, Significant figures = 3 in the Significant Figures Calculator (round & count) gives: Result: 1230; Scientific: 1.23×10³; E notation: 1.23e+3; ⚠ In the plain form 1230 it is unclear whether the trailing zeros are significant; use 1.23×10³ to show 3 significant figures; ℹ Rounded half-up on the decimal digits you typed, not through binary…

哪些输入会被检查？Which inputs are validated?

「有效数字计算器（修约 / 计数）」会检查这些输入——「有效数字位数」：必须填写；绝对值超过 10¹⁵ 的数也会被拒绝。不符合时结果区显示具体提示，不会给出数字。The Significant Figures Calculator (round & count) checks its inputs — "Significant figures": required; numbers above 10¹⁵ in absolute value are rejected too. When a value fails, the result area names the problem instead of showing a number.

有哪些选项可以调整？What options can I adjust?

「有效数字计算器（修约 / 计数）」的设置：「模式」可选 修约到 N 位有效数字、数有效数字（默认 修约到 N 位有效数字）；「数值」默认 1234.56；「有效数字位数」默认 3。每次生成结果都按当前设置处理。Settings in the Significant Figures Calculator (round & count) — "Mode": Round to N significant figures, Count significant figures (default Round to N significant figures); "Number" default 1234.56; "Significant figures" default 3. The result always uses the current settings.

计算精度如何？How precise are the results?

「有效数字计算器（修约 / 计数）」使用 JavaScript 双精度浮点数（约 15–16 位有效数字），部分功能使用 BigInt 处理大整数。The Significant Figures Calculator (round & count) uses double-precision floating point (about 15–16 significant digits); some features use BigInt for large integers.

「有效数字计算器（修约 / 计数）」免费吗？需要注册吗？Is the Significant Figures Calculator (round & count) free? Do I need an account?

「有效数字计算器（修约 / 计数）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Significant Figures Calculator (round & count) is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.