➗ 数学工具Math

百分比计算器Percentage Calculator

在线百分比计算：求某数的百分之几、占比多少、涨跌幅百分比。Calculate X% of Y, what percent X is of Y, and percentage change.

进制转换Number Base Converter

在线进制转换：二进制、八进制、十进制、十六进制及任意 2–36 进制互转，支持大数。Convert numbers between binary, octal, decimal, hex and any base 2–36 (big numbers supported).

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分数计算器Fraction Calculator

分数加减乘除计算，自动约分，显示带分数和小数结果。Add, subtract, multiply and divide fractions with simplification, mixed numbers and decimals.

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一元二次方程求解Quadratic Equation Solver

求解 ax²+bx+c=0，给出实数或复数根、判别式、顶点和对称轴。Solve ax²+bx+c=0 with real or complex roots, discriminant and vertex.

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最大公约数/最小公倍数GCD & LCM Calculator

计算多个整数的最大公约数（GCD）和最小公倍数（LCM），支持大数。Find the greatest common divisor and least common multiple of several integers (big numbers OK).

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质数判断与分解质因数Prime Checker & Factorization

判断一个数是否为质数，并分解质因数，显示所有因数。Check if a number is prime, factorize it and list all divisors.

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质数表生成器Prime Number List Generator

列出指定范围内的所有质数（埃拉托斯特尼筛法），统计个数。List all prime numbers in a range using the Sieve of Eratosthenes.

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阶乘计算器Factorial Calculator

计算 n!（支持到 5000!，大数精确结果），显示位数和末尾零个数。Calculate n! exactly (up to 5000!) with digit count and trailing zeros.

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排列组合计算器Permutation & Combination Calculator

计算排列数 nPr、组合数 nCr，以及可重复排列和可重复组合。Compute permutations nPr, combinations nCr, and with-repetition variants.

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统计计算器（平均数/中位数/标准差）Statistics Calculator (Mean, Median, SD)

输入一组数据，计算平均数、中位数、众数、方差、标准差、四分位数等。Compute mean, median, mode, variance, standard deviation, quartiles and more.

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科学计数法转换Scientific Notation Converter

数字与科学计数法、E 记数法、工程计数法互相转换。Convert numbers to scientific, E and engineering notation and back.

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罗马数字转换Roman Numeral Converter

阿拉伯数字与罗马数字互相转换（1–3999），自动识别输入。Convert between Arabic numbers and Roman numerals (1–3999), auto-detected.

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数字转英文单词Number to Words Converter

把数字转换为英文单词（如 1234 → one thousand two hundred thirty-four），含序数词和支票金额写法。Convert numbers to English words, ordinals and check-writing format.

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数字千分位格式化Number Formatter (Thousands Separator)

给数字添加千分位分隔符，按不同国家格式显示，以及万/亿和 K/M/B 缩写。Format numbers with thousands separators, locale styles, and compact forms (K/M/B, 万/亿).

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比例计算器Ratio Calculator

解比例方程 A:B = C:X，化简比例，按比例缩放尺寸（如 16:9）。Solve A:B = C:X, simplify ratios and scale dimensions (e.g. 16:9).

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勾股定理计算器Pythagorean Theorem Calculator

已知直角三角形任意两边，求第三边（a² + b² = c²），以及面积和角度。Find the missing side of a right triangle (a² + b² = c²), plus area and angles.

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三角形计算器Triangle Calculator

已知三条边求三角形面积（海伦公式）、周长、三个角和类型。Find triangle area (Heron's formula), perimeter, angles and type from three sides.

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圆计算器Circle Calculator

输入半径、直径、周长或面积中的任意一个，计算圆的其余参数。Enter radius, diameter, circumference or area to get the rest.

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体积计算器Volume Calculator

计算立方体、长方体、球体、圆柱、圆锥、棱锥的体积和表面积。Calculate volume and surface area of cube, box, sphere, cylinder, cone and pyramid.

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面积计算器Area Calculator

计算矩形、三角形、圆、梯形、椭圆、平行四边形等常见图形面积。Calculate the area of rectangles, triangles, circles, trapezoids, ellipses and parallelograms.

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对数计算器Logarithm Calculator

计算任意底数的对数 logₐ(x)，以及自然对数 ln、常用对数 lg 和 log₂。Calculate logarithms in any base, plus ln, log₁₀ and log₂.

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幂与开方计算器Exponent & Root Calculator

计算 x 的 y 次方和 x 的 n 次方根，大整数幂精确计算。Compute x to the power y and the nth root of x (exact big-integer powers).

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四舍五入计算器Rounding Calculator

按小数位或有效数字四舍五入，支持银行家舍入（四舍六入五成双）、向上、向下取整。Round numbers by decimals or significant figures: half-up, half-even (banker's), ceil, floor, truncate.

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加权平均数计算器Weighted Average Calculator

输入数值和权重，计算加权平均数，可用于计算学分绩点和综合评分。Calculate a weighted average from values and weights (grades, scores, portfolios).

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矩阵计算器Matrix Calculator

计算方阵的行列式、逆矩阵、转置和秩（最大 6×6）。Compute determinant, inverse, transpose and rank of a square matrix (up to 6×6).

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斐波那契数列计算器Fibonacci Calculator

计算第 n 个斐波那契数（大数精确），并列出前 n 项数列。Get the nth Fibonacci number (exact big integers) and list the sequence.

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小数转分数Decimal to Fraction Converter

把小数精确转换为最简分数（有限小数按 10ⁿ 约分），也可用近似模式把循环小数/无理数近似为分数，支持百分数。Convert decimals to exact simplest fractions (finite decimals via 10ⁿ), or approximate repeating decimals with a max denominator.

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线性方程组求解System of Linear Equations Solver

求解一元到六元一次方程组（高斯消元），每行输入一个方程的系数。Solve 1×1 up to 6×6 systems of linear equations (Gaussian elimination).

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二进制/十六进制计算器Binary & Hex Calculator

在二进制、八进制、十六进制下做加减乘除和位运算（AND、OR、XOR、移位）。Arithmetic and bitwise operations (AND, OR, XOR, shifts) in binary, octal or hex.

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Z 分数计算器Z-Score Calculator

根据数值、平均值和标准差计算 Z 分数，以及对应的百分位和左右尾概率。Z-score from value, mean and standard deviation, with percentile and tail probabilities.

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二项分布概率计算器Binomial Probability Calculator

计算 n 次独立试验中恰好、至多、至少成功 k 次的概率，以及期望和方差。Probability of exactly, at most and at least k successes in n trials, plus mean and variance.

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正态分布计算器Normal Distribution Calculator

计算正态分布在区间 [a, b] 内的概率、累积概率，以及给定概率对应的分位数。Probability between a and b for a normal distribution, cumulative probabilities and inverse (quantile).

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置信区间计算器Confidence Interval Calculator

根据样本均值、标准差和样本量计算均值的置信区间（使用 t 分布）。Confidence interval for a mean from sample mean, standard deviation and size (Student's t-distribution).

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样本量计算器Sample Size Calculator

计算调查所需样本量：置信水平、误差范围、预期比例和总体规模（有限总体修正）。Survey sample size from confidence level, margin of error, expected proportion and population size.

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线性回归计算器Linear Regression Calculator

输入 x、y 数据对，计算最小二乘回归直线 y = a + bx、相关系数 r 和决定系数 R²，可做预测。Least-squares regression line y = a + bx, correlation r and R² from x/y pairs, with prediction.

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有效数字计算器Significant Figures Calculator

统计一个数的有效数字位数，并按指定有效数字位数进行四舍五入（含科学计数法）。Count significant figures in a number and round it to a chosen number of sig figs.

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竖式除法计算器（带步骤）Long Division Calculator (with steps)

整数长除法，显示商、余数和每一步竖式计算过程，适合小学生学习。Integer long division showing quotient, remainder and every step — great for learning.

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计算 a mod n 的三种定义：向下取整（floor，结果与 n 同号，Python 的 %）、截断（truncated，结果与 a 同号，JS/C/Java 的 %）和欧几里得（结果总是非负），并给出对应的商，支持大整数。a mod n under three definitions — floored (sign of n, Python %), truncated (sign of a, JS/C/Java %) and Euclidean (always non-negative) — each with its matching quotient; BigInt supported.

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