Zellio.io

Percentage & Finance Calculator

Percentages, discounts, tip splits and loan EMI — all in one place.

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Frequently asked questions

What is an EMI?

An Equated Monthly Instalment is the fixed monthly payment on a loan covering both principal and interest. The calculator shows the monthly amount, total paid and total interest. EMI is the standard payment method for mortgages, car loans, and personal loans, and it ensures both lender and borrower know exactly what payment is due each month. The calculator breaks down how much of each payment goes toward principal (reducing the debt) versus interest (going to the lender), letting you understand the true cost of borrowing and compare loan terms.

Can it split a restaurant tip?

Yes — enter the bill, tip percentage and number of people to get the tip, total and each person's share instantly. This eliminates the awkward math of figuring out who owes what when splitting a check, especially with varied orders where some people had drinks or appetizers. Enter the total bill amount, your desired tip percentage (typically 15-20%), and the number of diners, and the tool calculates the per-person share including their portion of the tip. No more scrambling for calculators or mental math at the table.

Are my numbers private?

No. Everything runs locally in your browser using standard web APIs — your text, files and inputs are never uploaded to a server, so the tool works even offline once the page has loaded.

Pro tips

  • Divide, never subtract, when working backwards from a total to find the amount before tax or before a discount.
  • Compare loans on total interest paid rather than the monthly payment — a longer term lowers the monthly figure while costing considerably more overall.
  • Watch for stacked discounts: 20% off then a further 10% off is 28% off, not 30%, because the second applies to the reduced price.
  • State whether you mean percentage points or percent when reporting a change; the two differ by a factor that can be enormous.
  • For a tip split, agree whether the tip is calculated before or after tax before dividing — the two give different answers and both are conventional somewhere.

About Percentage & Finance Calculator

The loan figures use the standard amortising formula, where the monthly payment stays level while the split between interest and principal shifts across the term. That is why total interest, rather than the monthly number, is the figure worth comparing between two offers.

Work out percentages and percentage change, sale discounts and final prices, tip splits per person, and monthly loan or EMI payments with total interest — all in one place. It covers the everyday money maths that comes up while shopping, dining out, budgeting and comparing loans.

Switch between modes to answer 'what is X% of Y', 'how much do I save', 'what is each person's share' or 'what will this loan cost'. Percentage change is the one to double-check: 40 rising to 50 is a 25% increase, while 50 falling back to 40 is a 20% decrease.

Two percentage mistakes are common enough to be worth naming. The first is confusing a percentage change with a percentage point change: a rate moving from 2% to 3% is a rise of one percentage point and an increase of fifty percent, and both statements are true of the same movement. The second is assuming changes cancel — an item discounted 20% then raised 20% does not return to its original price, because the increase is calculated on the smaller figure. £100 becomes £80 and then £96.

Reversing a percentage is the operation people most often get backwards. To find the pre-tax figure inside a £120 total at 20% tax, you divide by 1.2 to get £100; subtracting 20% of £120 gives £96 and is simply wrong. The same applies to working out an original price from a sale price. Whenever you are undoing a percentage rather than applying one, the operation is division.

Common use cases

  • Working out the real saving on a sale item, especially when discounts are stacked.
  • Splitting a restaurant bill with a tip across an uneven group.
  • Comparing two loan or finance offers on total cost rather than the advertised monthly payment.
  • Backing out the pre-tax amount from an invoice total for expenses or bookkeeping.
  • Checking a reported percentage change in a report or news story that sounds implausible.
How it comparesA spreadsheet handles all of this and requires you to write the formula correctly, which is where the reversal errors happen. Dedicated loan calculators from lenders tend to foreground the monthly payment; seeing total interest alongside it is what makes two offers comparable.