🔢 数根（数字根）Digital Root Calculator
反复把各位数字相加直到只剩一位；也等于 1 + (n - 1) mod 9。支持很长的整数。本地处理。Repeatedly add the digits until one digit remains; equals 1 + (n - 1) mod 9. Works with very long integers. Processed locally.
使用说明与常见问题How-to & FAQ
「数根（数字根）」是什么？What is the Digital Root Calculator tool?
反复把各位数字相加直到只剩一位；也等于 1 + (n - 1) mod 9。支持很长的整数。本地处理。Repeatedly add the digits until one digit remains; equals 1 + (n - 1) mod 9. Works with very long integers. Processed locally.
如何使用「数根（数字根）」？How do I use the Digital Root Calculator tool?
填写一个非负整数（很长的数字也可以），即可得到数字根：反复把各位数字相加直到只剩一位。结果会随输入实时更新。Enter a non-negative integer (very long numbers are fine) to get its digital root, found by adding the digits repeatedly until one digit remains. The result updates as you type.
用途？Uses?
常用于"弃九法"验算加法和乘法。Handy for casting out nines to check sums and products.
能举个计算实例吗？Can you show a worked example?
例如在「数根（数字根）」中填 非负整数 = 987654321，结果区显示：数根：9；过程：987654321 → 45 → 9For example, entering Non-negative integer = 987654321 in the Digital Root Calculator gives: Digital root: 9; Steps: 987654321 → 45 → 9
有哪些选项可以调整？What options can I adjust?
「数根（数字根）」的设置：「非负整数」默认 987654321。每次生成结果都按当前设置处理。Settings in the Digital Root Calculator — "Non-negative integer" default 987654321. The result always uses the current settings.
计算精度如何？How precise are the results?
「数根（数字根）」使用 JavaScript 双精度浮点数（约 15–16 位有效数字）；极大或极小的数值可能存在精度误差。The Digital Root Calculator uses double-precision floating point (about 15–16 significant digits); very large or very small values may lose precision.
「数根（数字根）」免费吗？需要注册吗？Is the Digital Root Calculator free? Do I need an account?
「数根（数字根）」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 Digital Root Calculator is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.