Time guide
Percentage Change Calculator: Work Out a Rate Increase, Discount, or Fee (Free Tool)
Work out a rate increase, discount, or fee with the free percentage change calculator.
Freelancers run into percentage math constantly — "how big a raise is going from $50/hr to $65/hr?", "what's a project fee after a 15% discount?", "what's the referral fee on this invoice?" TidyPapers' Percentage Change Calculator at https://tidypapers.com/percentage-change-calculator/ covers three different versions of that question, each as its own mode. This guide explains every field in every mode.
What this tool is for
It has three separate modes, because "percentage change" actually means three different calculations depending on what you already know and what you're trying to find. Pick the mode that matches your situation.
Mode 1 — From A to B (find the percent change between two numbers)
Use this when you know a starting value and an ending value, and want to know the percentage change between them.
Step 1 — Enter the two values
- Before (A) — the starting value (e.g. your old hourly rate).
- After (B) — the ending value (e.g. your new hourly rate).
On the live toolthe Before (A) and After (B) fields filled in
Step 2 — Read the results
The tool shows three outputs:
- Absolute change — the plain difference between the two numbers
- Percent change — the percentage increase or decrease
- Tidied result — a cleaned-up, rounded version of the percentage for easy reading
On the live toolthe Absolute change, Percent change, and Tidied result outputs
The page gives a worked example for this exact situation: "You charged $50/hr and now charge $65/hr: this tool tells you that's a +30% raise." It also flags an easy mistake to make — the calculation is not symmetric. Going from 50 to 65 is +30%, but going back from 65 to 50 is not −30%; it's "about −23.08%." Always check which direction you're measuring.
Mode 2 — A changed by D% (find the new value after a known percentage change)
Use this when you know a starting value and the percentage it's changing by, and want the resulting new value.
Step 1 — Enter the values
- Starting value (A) — the number you're starting from.
- Percent change (D%) (signed, e.g. -15) — the percentage to apply. Use a negative number for a decrease (e.g. a discount) and a positive number for an increase (e.g. a markup or raise). The field label itself gives the example format: "-15".
On the live toolthe Starting value (A) and signed Percent change (D%) fields filled in, with a negative example like -15
Step 2 — Read the results
- New value — the resulting number after the percentage change is applied
- Absolute change — the plain-number difference caused by that change
On the live toolthe New value and Absolute change outputs
The page's own example: "a $200 project fee cut by 15% becomes $170." This is the mode to use for applying a discount or a price increase to a known starting number.
Mode 3 — What is D% of A (find a straight percentage of a value)
Use this when you just need to work out a percentage amount of a number — for example, a referral fee or commission.
Step 1 — Enter the values
- Percent (D%) — the percentage rate (e.g. "12" for 12%).
- Of value (A) — the number you're taking that percentage of (e.g. an invoice total).
On the live toolthe Percent (D%) and Of value (A) fields filled in
Step 2 — Read the result
- Result — the calculated amount.
On the live toolthe Result output
The page's worked example: "a 12% referral fee on an $850 invoice is $102."
Other situations the page addresses
The page also notes what happens when your starting value is zero or when you're comparing against a free period — for example, it mentions "a free trial period" transitioning to paid rates as a case where percentage-change math behaves unusually (a change from $0 has no meaningful percentage, since you can't divide by zero), so treat that kind of before/after as a plain dollar difference rather than a percentage.
Which mode should I use for which freelance situation?
| Situation | Mode to use |
|---|---|
| "How much of a raise is my new rate vs my old rate?" | Mode 1 — From A to B |
| "What does my fee become after a 15% discount?" | Mode 2 — A changed by D% |
| "How much is my referral fee/commission on this invoice?" | Mode 3 — What is D% of A |
Frequently asked practical questions
Can I use this to check a payment processor's fee?
Yes — Mode 3 works for that (percent of an invoice amount), though the dedicated Payment Fees Comparison tool is built specifically for comparing processors side by side and is a better fit if you're choosing between them.
Does this tool save any numbers I enter?
No — it calculates in your browser only; nothing is stored or sent anywhere.
Why isn't going from 65 back to 50 a −30% change?
Because percentage change is always measured relative to the starting number, and the starting number is different in each direction (50 in one case, 65 in the other) — this is a common source of confusion the tool's own example specifically calls out.