Phone Plan Calculator: Which Plan Actually Costs Less? - 9314 Toolbox - Where the lines cross, that's your answer

1. An interactive lesson, not a static calculator

Choosing between two phone plans is really a linear-function problem: Plan A has a cheap monthly fee but expensive minutes; Plan B is the opposite. Which one wins depends entirely on how many minutes you use each month.

The page opens with the givens and the question. Then don't rush into algebra — drag the slider first and watch the distance between the two dots. The moment they touch, the break-even point reveals itself.

2. What everything on the chart means

The horizontal axis is monthly minutes; the vertical axis is that month's total cost. The orange line is Plan A, the blue line is Plan B, and the dashed vertical line is the usage you dragged to. The pale shading marks each plan's territory, and the crossing point is the break-even line.

The equation chips at the bottom update live: what A costs, what B costs, the difference, and who to pick.

3. Where the break-even point comes from

Set the two costs equal: 20 + 0.25x = 50 + 0.1x. Rearranging gives 0.15x = 30, so x = 200 minutes, where both cost $70. Another way to see it: B's extra $30 monthly fee has to be earned back at $0.15 saved per minute — 30 ÷ 0.15 = 200 minutes.

This isn't a conclusion you just read — hit "Change rates", tweak the fees and per-minute prices any way you like, and the crossing point re-positions instantly to verify the formula.

FAQ

Where do I find my monthly minutes? Check your carrier's app for the monthly usage summary, and average the last two or three months for a steadier picture. Plans with off-peak or weekend rates don't fit this simple model.

What about data? This page models the simplest case: monthly fee + per-minute price. You can fold a data difference into the monthly fee — if B charges $10 more for data, set B's fee 10 higher. The reasoning is identical.

Is anything uploaded? No. Charting and math happen entirely in your browser. The page makes no network requests and needs no account.

Tool: Phone plan calculator. Chinese version: 手机套餐怎么选最划算