We are the MonoTape team. Before you set a price or say yes to a discount, there is one number you really want to know: what is the profit, and the margin, at that price? Walk into a negotiation without it and you can agree to a cut that quietly erases your margin. The math is two short steps — price minus cost is profit, profit divided by price is margin — but on a plain calculator each new price means doing both again from scratch, with nothing labeled. The risk is not the arithmetic; it is not seeing the margin move as the price does.
Profit and margin depend on the price, so they should move with it
When you are pricing something, you are usually trying prices: what if I sell at $50, at $45, at $40? At each one you need the profit and the margin to decide if it is still worth it. A standard calculator computes 50 - 32, then 18 / 50, and gives you two numbers — but it forgets them the moment you try the next price, and there is no label saying which was profit and which was margin.
A notes app will hold the figures but will not do the division, so the percentages get worked out somewhere else and stale fast. What pricing really needs is a place where price, cost, profit, and margin all sit on labeled lines that depend on each other, so changing the price flows straight through to the margin.
Work back from price to profit to margin
This is exactly the kind of dependent, what-if math we built MonoTape for. You put price and cost on labeled lines, then derive profit and margin from them by reference, so the chain stays connected.
For an item that costs you $32, sold at $50, the tape reads:
Now the whole picture is on one tape: the price, the cost, the $18 profit, and the 36% margin, each clearly named. Before a discount conversation you can see exactly how much room you have, instead of guessing and hoping. The margin is not a number you computed once and forgot — it is sitting there, tied to the price.
Drop the price and watch the margin react
Here is where it pays off in a negotiation. The buyer asks for $45. On a calculator you redo both steps; here you rewrite the Price line and the profit, then the margin, recalculate on their own. You see in real time that $45 still leaves a 28.9% margin, so you know whether you can say yes — or where to hold the line.
Pricing and margin are a tool problem, not a math problem. Put price and cost on labeled lines, derive profit and margin by reference, and change the price to watch the margin move. It all saves locally on your device, so your pricing scratchpad is there before every negotiation. For the related case of stacked discounts, see how to get the percent-off price right, and to flip between figures with and without tax, read how to get price with tax and before tax in seconds.
MonoTape
A calculator notepad where you label your math and one edit recalculates everything. Margins, work quotes, event budgets — whatever you calculate stays on the tape. Free to use.
Learn more about MonoTapeFrequently asked questions
Can profit and margin update when I change the price?
Yes. Derive profit and margin from the price and cost lines by reference. Edit the price and both the profit and the margin recalculate automatically, so you see the trade-off instantly.
Can I work backward from a target margin?
You can try prices and watch the margin land where you want, adjusting the price line until the margin line shows your target. Because everything recalculates live, finding the right price is quick.
Will my pricing scratchpad still be there next time?
Yes. The tape is saved locally on your device, so your pricing setup is ready before the next negotiation. Nothing is uploaded anywhere.
Is it free?
Yes. Labeled calculations, references, auto-recalculation, and tape-style history — every feature mentioned here is free. It works on both iPhone and Android.