Personal finance calculators

Loans, returns, budgets and savings. Each one shows the formula, where it comes from and how to work it out by hand, because a number you cannot check is a number you cannot trust.

• Simple Interest Calculator 1,000 at 5% simple interest earns 50 a year, every year, so 500 over a decade. Compound interest on the same terms would have earned 628.89. Work out both and see the gap.
• Loan Calculator Borrow 15,000 at 8% over 5 years and you pay 304.15 a month, of which 100 is interest in the very first payment and barely 2 in the last. Work out the payment, the total cost and how it splits.
• Amortization Schedule Calculator On 150,000 at 4% over 30 years the payment is 716.12, and you repay 257,804 in total. The first payment is 500 interest; the last is 2.38. See the full schedule year by year.
• Constant Principal Loan Calculator On 150,000 at 4% over 30 years, the first payment is 916.67 and the last is 418.06. You pay 90,250 in interest instead of 107,804 — 17,554 less than a level-payment loan.
• Interest-Only Loan Calculator 150,000 at 4% interest-only costs 500 a month — and 150,500 in the final month. Over 30 years the interest reaches 180,000, which is 72,196 more than a repayment loan.
• Mortgage Overpayment Calculator A 10,000 overpayment one year into a 150,000 mortgage at 4% saves 19,361 in interest and removes 41 payments. The same 10,000 later saves far less.
• Debt-to-Income Calculator On 2,500 a month with no existing debt and a 35% limit, you can take on 875 in payments and keep 1,625 to live on. Add existing debts and watch the headroom close.
• Home Affordability Calculator On 2,500 a month with 60,000 saved, you can afford a 200,000 home at 3.5% over 30 years — and here the deposit is the binding constraint, not the payment.
• Debt Snowball Calculator Three debts totalling 9,800 with 100 extra a month. Snowball clears the smallest first and takes 29 months; avalanche clears the dearest first and takes 28, saving 283 in interest. Compare both on your own numbers.
• APY Calculator A 6% nominal rate compounded monthly is really 6.17% a year. Add fees and it climbs further. The advertised rate is never the rate you pay or earn.
• Savings Goal Calculator To reach 20,000 in ten years starting from 2,000 at 5%, you need 107.58 a month. You put in 14,910 and the interest supplies the remaining 5,090.
• CD and Term Deposit Calculator 10,000 locked away for 12 months at 3% earns 300 gross, but 243 after a 19% withholding. The advertised rate is never the rate you keep.
• Emergency Fund Calculator With 1,500 a month in expenses, six months of cover means a fund of 9,000. If you have 3,000 and save 250 a month, you are two years away.
• Retirement Calculator Saving 300 a month from 35 to 65 at 6% builds 391,693 — but that is 161,372 in today's money, and it pays about 1,040 a month in today's terms. Both numbers matter.
• Future Value Calculator 1,000 at 5% compounded monthly becomes 1,647 in ten years, not 1,500. The compounding frequency is what turns a 5% headline rate into an effective 5.12%.
• Present Value Calculator 10,000 promised in ten years is worth 6,139 today at a 5% discount rate. Waiting costs you 3,861 in present-day terms.
• NPV Calculator Invest 1,000 and get 400 back for three years, and at a 10% discount rate the NPV is −5.26. It looks like a 20% profit and it destroys value.
• IRR Calculator 1,000 invested returning 400 a year for three years has an IRR of 9.7%. If you demand more than that, the project is not worth doing.
• Payback Period Calculator 1,000 returning 400 a year is paid back in 2.5 periods. Discount those flows at 10% and it is never paid back at all — which is the more useful answer.
• Rule of 72 Calculator At 5% a year, money doubles in about 14.4 years: that is 72 divided by 5. The exact answer is 14.21, so the shortcut is off by roughly ten weeks.
• Inflation Calculator At 3% a year for ten years, 1,000 buys what 744 buys today: a 25.6% loss. Meanwhile, what costs 1,000 now will cost 1,344.
• Cumulative Inflation Calculator Four years of 5%, 8%, 3% and 2% inflation is not 18% but 19.14%, because each year compounds on the last. Enter the actual yearly figures and get the real total.
• Credit Card Interest Calculator A 2,000 balance at 24% APR, paying 150 a month, takes 16 months and costs 350 in interest. Raise the payment and watch both numbers collapse.
• Minimum Payment Calculator Paying only the 3% minimum on a 2,000 balance at 24% APR takes over eight years and costs more than 1,500 in interest. The minimum is designed to keep you paying, not to clear the debt.
• Cash vs Financing Calculator 1,200 cash, or 110 a month for 12 months. That is 1,320 — 120 more, which is a real interest rate of 19.5% a year, not the 10% it looks like.
• ROI Calculator Turning 1,000 into 1,500 is a 50% ROI, but spread over ten years that is only 4.14% a year. Work out both, because the second one is what lets you compare.
• CAGR Calculator Growing from 1,000 to 1,500 in ten years is 50% total growth, but a CAGR of 4.14% a year, not the 5% you get by dividing. Work out the rate that actually compounds.
• Dividend Calculator 100 shares paying 0.50 quarterly is 200 gross a year, or 162 after 19% tax. That is 13.50 a month and a 5% yield at a 40 share price.
• Dividend Yield Calculator A share at 40 paying 0.50 quarterly yields 5%. If you bought it at 25, your yield on cost is 8% — same dividend, different denominator.
• Dollar Cost Averaging Calculator Investing 100 at prices of 10, 8, 12, 9 and 11 gives an average paid of 9.80, below the 10.00 average of the prices themselves. Buying a fixed amount buys more units when it is cheap.
• Brokerage Fee Calculator A 1,000 trade at 0.2% with a 5 minimum costs 5 each way, so 10 round trip. The position has to rise 1% before you are even.
• Average Cost Basis Calculator Buying 10 at 25, 20 at 18 and 15 at 22 gives an average of 20.89, not the 21.67 you get by averaging the three prices. Size weights the answer.
• Risk Reward Ratio Calculator Entering at 50 with a 5% stop and a 15% target gives a 3-to-1 ratio, which means you only need to be right 25% of the time to break even.
• Position Size Calculator With 10,000 in capital risking 1% per trade, entering at 50 with a stop at 45, you buy 20 units. The most you lose is 100, whatever the position is worth.
• Margin Call Calculator 1,000 at 30x leverage controls a 30,000 position, and every 1% move swings your account by 30%. A fall of just 1.67% closes you out.
• Tip Calculator A 50 bill with an 18% tip comes to 59, which is 29.50 each between two. Split the bill and the tip in one go.
• 50/30/20 Budget Calculator On 2,000 a month, the rule puts 1,000 towards needs, 600 towards wants and 400 into savings, which is 4,800 a year. Split your pay into the three buckets.
• Forex Lot Size Calculator With a 10,000 account risking 1% and a 20-pip stop, you can trade 0.5 lots. Each pip is then worth 5, so the stop costs exactly the 100 you were willing to lose.
• Maximum Drawdown Calculator An equity curve peaking at 12,800 and falling to 9,600 is a 25% drawdown — and getting back needs a 33.3% gain, not 25%. Losses and recoveries are not symmetric.
• Pivot Point Calculator A period with a high of 110, a low of 90 and a close of 105 gives a pivot at 101.67, with resistance at 113.33 and support at 93.33. Traditional, Camarilla and Woodie from the same candle.
• Fibonacci Retracement Calculator A move from 100 to 200 puts the 61.8% retracement at 138.20, the 50% at 150 and the 38.2% at 161.80. All the levels, plus the extensions beyond the move.
• Sharpe Ratio Calculator Enter a series of returns and get the Sharpe ratio, which measures return per unit of risk, alongside the Sortino, which only counts the falls.
• ATR Calculator Enter your candles as high/low/close and get the average true range, plus a stop set at a multiple of it — a stop that adapts to how much the asset actually moves.
• Historical Volatility Calculator Enter a series of closing prices and get the annualised volatility, along with what counts as a normal move and what counts as a bad day.
• Interest Rate Converter Convert an interest rate between nominal and effective and between any two periods. A 60 % nominal rate compounded monthly is not a 60 % effective rate, and the gap is twenty points.
• FIRE Calculator How large a portfolio it takes to live off it, and how many years it takes to get there. Under the 4 % rule, twenty-five times what you spend in a year.
• Fixed vs Variable Mortgage Calculator Compares what you end up paying on a fixed-rate mortgage and on a variable one, with the rate review after the introductory period. It is a scenario, not a forecast: nobody knows the future index.
• Lease vs Buy Calculator Leasing against buying with finance. The honest comparison is not payment against payment: at the end of the term the car you bought is yours and worth something, and the leased one is not.
• Annuity Payout Calculator How much you can draw each month from a capital sum over a number of years without it running out early, and how much you could draw without touching the capital at all.
• Early Payment Discount Calculator Two per cent for paying in ten days instead of thirty sounds trivial and works out at around 37 per cent a year. This calculator puts that number on it, and that is the number that decides.
• Crypto Profit and Loss Calculator The real gain or loss on a trade, after the fees on both sides and the tax. It works the same for cryptocurrency and for shares.
• Opportunity Cost Calculator What a purchase really costs is not what you pay but that plus what the money would have earned. This shows the second part, the one that never appears on the receipt.
• How Long to Reach Your Savings Goal How long it takes to reach an amount saving the same figure every month. It is the reverse of the required-saving question: there you pick the term, here you pick the contribution.
• Daily Expense Savings Calculator The daily coffee, the cigarettes or any small repeated expense: what it adds up to in a year and what it would become if you invested it instead.
• Life Insurance Cover Calculator How much cover a life policy should provide, using the DIME method: debts, income to replace, mortgage and children's education, less what you already have.
• Currency Exchange Fee Calculator How much you actually receive when changing currency and what the operation costs you, counting the spread against the mid-market rate, which is where the unadvertised cost nearly always sits.
• Rent vs Buy Calculator Renting against buying, comparing what leaves your pocket either way and what you are left with at the end. The deposit you do not put into a house gets invested, and that counts too.
• Rental Yield Calculator The yield on a rental property, gross and net. Gross is the one that gets advertised and net is the one you collect, and there are usually a good two points between them.
• Asset Depreciation Calculator Asset depreciation by the three classic methods, with the year-by-year table. Straight line spreads it evenly and the other two front-load it, which is when an asset actually loses value.
• Fund Fee Impact Calculator One per cent a year in fees sounds like nothing and over thirty years takes roughly a quarter of everything you would have gained. This puts that figure on it.
• Service Charge Split Calculator Splits a building's shared cost according to each flat's ownership share, which is set in the deeds and is not the same for everyone.
• Debt Consolidation Calculator Whether refinancing your debts with a new loan is really worth it: compare what you have left to pay today with what you would pay on the new one, and see the trap in the lower payment.
• Home Buying Costs Calculator Adds up everything paid on top of the price when buying a home — tax, notary, registry, agency and valuation — and tells you how much saving it takes to complete.
• Payment Processing Fee Calculator Works out what you keep from a payment through Stripe, Square, Mercado Pago or any processor that charges a percentage plus a fixed amount, and how much to charge to receive a net amount.