Percentage Calculator
Quick and easy percentage calculations for everyday use.
Other Professional Calculators
Why I keep building calculators
I once sent a client an invoice with the wrong tax and got the politest “are you sure?” you can imagine. Tomato face. To avoid doing that again, I started running every discount, tip, rent bump, and quick price check through a calculator I trust.
More oddities kept showing up: loyalty promos stacking strangely, VAT pulled out the wrong way, shipping added before discounts, and “limited” sales that were mostly optimistic rounding. Each time I tripped, I saved a note and added an example here. It reads like a journal because it is one.
Funniest miss so far: a “35% off” jacket that was really 20% off plus 15% hope from the marketing team. The receipt was a great teacher.
That habit snowballed: after percentages came finance, real estate, education, freelance rates, each built after a real facepalm. If these stories help you dodge a bad total or at least smile once, they’ve done their job.
Quick way to use it
- Pick a mode: percent of number, reverse percent, change %, markup/discount, or compound interest.
- Type numbers as you see them; decimals welcome.
- Glance at the formula under the result; adjust if it feels off.
- Save to history only if you want—data stays in your browser.
Shortcut: Tab through fields, hit Enter. No magic, just math.
Freelance invoice check
€1,200 + 19% tax − 3% platform fee → €1,385.16 net. If the margin drops under 30%, I renegotiate before typing “sure!”.
Mortgage comparison
$220k at 6.10% vs 5.70%: $56/month apart, ~$16.8k over 25 years. Tiny rates, big lifetime gap.
Discount sanity check
Shelf $55, sale $44 → 20% off, not “up to 35%.” If I wanted more, I wait and keep my wallet closed.
Common mistakes to avoid
- Remove VAT right:
Total ÷ 1.19for 19% VAT. - Apply discounts before shipping, not after.
- Keep rate units aligned (annual with years, monthly with months).
- Round at the end, not mid-calculation.
Quick formulas I reach for
Who it helps
Students checking grades, freelancers pricing work, small shops testing discounts, friends splitting bills, and anyone who wants a quick confidence check without opening a spreadsheet.
Privacy in plain words
- History lives in your browser (localStorage). Clearing your cache erases it.
- No tracking pixels or pop-ups.
- Formulas stay visible so you can double-check the math.
A week of real calculations
Monday: monitor $389 with 12% coupon → $342.32. Tuesday: retainer $1,400 → $1,610 (+15%). Wednesday: “3 for 2” vs 25% off—25% wins. Thursday: add-on bag made a budget flight 18% more. Friday: student loan 6.8% monthly compounding—$50 extra/month shortens payoff. Saturday: uneven dinner bill—percent share kept it fair. Sunday: hosting $49 → $63 (+28.5%) so I downgraded.
Quick FAQs
Yes. No sign-up or email capture.
They stay in your browser if you save history. Nothing leaves your device.
Send the exact inputs on the Contact page and I’ll fix it quickly.
About the builder
I’m Daniel, a developer who hates bad math on receipts. I answer feedback fast—usually the same day. If something feels off,tell me and I’ll sort it out.