Money questions,
clearly answered.
PlainSums turns the big money decisions — mortgages, loans, saving, retirement — into a clear, itemized answer. No jargon, no sign-up, and we always show our work.
- Free, no sign-up
- Nothing stored — math runs in your browser
- Every figure itemized
- Principal & interest
- $2,022.62
- Property tax
- $366.67
- Insurance
- $125.00
- Loan amount
- $320,000
- 27
- Free calculators, no sign-up
- 5
- Money areas, one hub
- $0
- Cost — and nothing stored
- 100%
- Itemized — we show the math
Five areas, 27 calculators
Each one shows the full breakdown behind the number — not just a single figure.
Work out what a home really costs — payment, affordability and whether to rent or buy.
- Mortgage
- Affordability
- Rent vs Buy
- Refinance
- Extra payments
Plan a loan, compare payoff strategies, and see the true cost of what you borrow.
- Loan
- Auto loan
- Credit card
- Debt payoff
Watch compounding do the heavy lifting and map the path to a savings goal.
- Compound interest
- Savings goal
- Investment
- FIRE number
- Millionaire
- With withdrawals
- Dividend
- Roth IRA
- 529 plan
- CD
Project what your nest egg becomes and how long it can last.
- Retirement
- Withdrawal
- Retirement income
- Coast FIRE
- Barista FIRE
Translate a salary into take-home pay and settle the everyday math.
- Take-home pay
- Salary ↔ hourly
- Tip & split
We show the math
Every result is a statement: the bottom-line figure, then every line that built it — principal, interest, tax, growth. No black boxes.
Start here
Mortgage Calculator
Enter a home price, down payment and rate to see your full monthly payment — principal, interest, property tax and insurance — plus how much interest you'll pay over the life of the loan.
OpenLoan Calculator
Works for any fixed-rate loan. Enter the amount, rate and term to see your monthly payment and exactly how much the loan costs in total.
OpenCompound Interest Calculator
Compounding is interest earning interest. Set a starting balance, a monthly contribution and a rate to watch your money grow — and see how much of the result is pure growth.
OpenRetirement Calculator
Project your nest egg to retirement age, including any employer match, and see the annual income it could safely provide.
OpenTake-Home Pay Calculator
A quick estimate of what lands in your account after federal and state tax, FICA, and pre-tax retirement contributions. For planning, not payroll.
OpenMoney guides
How Much House Can You Really Afford?
A plain-English guide to working out a home price you can comfortably afford — the 28/36 rule, down payments, and the costs people forget.
Mortgage Amortization, Explained
Why your early mortgage payments are almost all interest, how the balance falls over time, and what extra payments actually do.
Debt Snowball vs. Avalanche: Which Wins?
The two most popular debt-payoff strategies compared — which saves the most money, which keeps you motivated, and how to choose.
The 4% Rule, Explained
What the 4% rule is, where it came from, its limits, and how to use it to size the nest egg you need for retirement or financial independence.