下表列出了所有Tcl语言支持的算术运算符。假设变量A=10，变量B=20，则：
| 运算符 | 描述 | 例子 |
|---|---|---|
| + | 两个数相加 | A + B = 30 |
| - | 第一个操作数减去第二个操作数 | A - B = -10 |
| * | 两个操作数相乘 | A * B = 200 |
| / | 分子(B)除以分母(A) | B / A = 2 |
| % | 模运算和整数除法后的余数 | B % A = 0 |
试试下面的例子就明白了所有Tcl语言中可用的算术运算符：
#!/usr/bin/tclsh set a 21 set b 10 set c [expr $a + $b] puts "Line 1 - Value of c is $c\n" set c [expr $a - $b] puts "Line 2 - Value of c is $c\n" set c [expr $a * $b] puts "Line 3 - Value of c is $c\n" set c [expr $a / $b] puts "Line 4 - Value of c is $c\n" set c [expr $a % $b] puts "Line 5 - Value of c is $c\n"
当编译和执行上面的程序，它会产生以下结果：
Line 1 - Value of c is 31 Line 2 - Value of c is 11 Line 3 - Value of c is 210 Line 4 - Value of c is 2 Line 5 - Value of c is 1
