Sumslip

Independent money math

Money math you can check.

Sumslip is a set of calculators for saving, borrowing, and everyday prices. Each page shows the formula, uses the numbers you type, and does not ask you to open an account.

Grow

Future value, a savings target, retirement balances, return, and inflation.

  1. 01Compound interestFuture value of a starting balance plus a monthly deposit.
  2. 02Savings goalThe deposit, or the time, that reaches a target balance.
  3. 03Retirement balanceA nest egg at a chosen age, in future money and today's money.
  4. 04Return on investmentSimple return and compound annual growth from a start and an end value.
  5. 05InflationFuture cost of today's amount, or today's value of a future amount.

Borrow

Installment loans, a mortgage payment, and a credit-card payoff.

  1. 01Loan paymentLevel payments or equal principal, with an optional extra payment.
  2. 02MortgagePrincipal and interest, plus the tax, insurance, and dues you type.
  3. 03Credit card payoffMonths and interest to clear a revolving balance with a fixed payment.

Everyday

Percentages, pay, discounts, sales tax or VAT, splitting a bill, and a separate tip calculator.

  1. 01PercentagePercent of an amount, a ratio, a change, or add and subtract a percent.
  2. 02Salary and hourlyConvert annual pay and an hourly wage using hours and weeks you choose.
  3. 03DiscountTwo markdowns in a row, then a tax on the sale price.
  4. 04Sales tax and VATAdd a tax rate, or pull a tax rate back out of a total.
  5. 05Split a billTax and a per-person share. No tip.
  6. 06TipTip and tax for a place where people tip, then split the total.

How to choose a calculator

Pick the page that matches the decision

Growing a balance, paying a debt, and splitting a bill are different formulas. A compound-interest page will overstate the cost of a loan, because a loan balance falls as you repay it. A loan page will understate a savings plan, because it does not add a monthly deposit.

Currency on the page is a label and a rounding rule. US dollars, euros, and British pounds round to two decimal places. Won and yen round to the whole unit. Changing the currency does not convert the amount. Type the number in the unit you have in mind, or convert it before you start.

Numbers this site does not look up

Sumslip does not look up today's mortgage rate, exchange rate, or tax bracket. Those figures change, and a stale table would pretend to be an official answer. You type the rate from your own statement, offer, or tax notice.

The site also does not rank lenders or cards. There is no paid placement inside a result.