An arithmetic progression is a list of numbers where each step is the same size — 3, 7, 11, 15, each term 4 more than the last. That constant step is called the common difference, and once you know the first term and the difference, the entire sequence is determined: the nth term is a₁ + (n-1)d, and the sum of the first n terms is (n/2)(2a₁ + (n-1)d). The young Gauss famously summed 1 to 100 in seconds by pairing numbers (1+100, 2+99, ...), each pair totaling 101 — that pairing trick is the sum formula in disguise. Arithmetic progressions model anything growing by steady increments: simple-interest balances, fixed-amount savings plans, and evenly spaced fence posts. This calculator runs the progression math for you: enter your values in the Variable A and Variable B fields and read the Result. The key thing to internalize is linearity — graph the terms and they fall on a perfectly straight line, which is what separates arithmetic sequences from their curvier geometric cousins.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Arithmetic Progression Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.