Methodology: Every Formula on LifeCost

Each calculator on this site publishes the arithmetic it runs. This page collects every formula in one place, linked to the calculator that uses it. If a formula and its page ever disagree, that is a bug: report it.

Financial Audit

The Financial Audit: Net monthly cash flow = take-home income − rent − subscriptions − food delivery − other expenses − credit card interest. Real net worth = savings + car value − credit card debt − car loan balance. Grade starts at A and drops if cash flow or net worth turn negative, with extra penalties for deep deficits.

Debt & Purchase Calculators

Credit Card Interest Shock + Event Adder: Minimum payment = max(balance × minimum %, floor amount). Each month interest = balance × APR ÷ 12. The tool loops payments until every card balance hits zero and totals combined months, interest, and the added cost of the extra purchase.

Car Payment vs Income + Negative Equity: Payment percentage = monthly payment ÷ monthly take-home income × 100. Negative equity = loan balance − car value. Break-even months are estimated using the portion of the payment that goes to principal after interest.

Wants vs Debt: Monthly credit card interest = balance × APR ÷ 12. The verdict compares monthly wants to monthly interest.

Hours of Life / Barista Converter: After-tax hourly wage = gross wage × (1 − tax rate ÷ 100). Hours to afford the item = item cost ÷ after-tax hourly wage.

Debt Snowball vs Avalanche: Snowball pays the smallest balance first. Avalanche pays the highest APR first. Both pay minimums on all other debts and apply the extra cash to the target debt.

Can I Afford It? Flowchart: Affordability depends on whether the price fits your income after expenses, whether you have an emergency fund, and whether high-interest debt is paid off.

Compound Interest Grapher: Each month: balance = (balance + monthly addition) × (1 + annual rate ÷ 12 ÷ 100). The loop repeats for the chosen number of years.

Event Debt Adder: New balance = current balance + event cost. The tool runs the credit card minimum-payment loop on both the old and new balance and reports the difference in months and total paid.

True Cost Time Calculator: Hours = item cost ÷ gross hourly wage.

Credit Score Drop Simulator: New score = current score − sum of selected point penalties. Penalties are fixed: missed payment −80, maxed card −45, new inquiry −5.

Daily Frugality Calculators

Food Delivery Annual Drain: True order cost = subtotal × (1 + markup% + service% + tip%) + delivery fee. Weekly cost = true order cost × orders per week. Annual cost = weekly × 52 + subscription × 12.

Pantry Meal Value: Savings = comparable fast food cost. Pantry ingredient cost is treated as $0 because they are already owned.

Tap Water vs Bottled Water Drain: Bottled annual = cases per month × cost per case × 12. Filter annual = filter cost + refills × refill cost × 12.

SNAP Food Stamp Pacer: Days left = days in month − current day. Daily limit = remaining balance ÷ days left.

Fast Food Value Finder: Best value = lowest combined normalized cost per 1000 calories and cost per 100g protein. Cost per 1000 calories = (1000 ÷ calories) × cost; cost per 100g protein = (100 ÷ protein) × cost.

Ramen vs Bulk Rice Timeline: Ramen daily cost = pack cost ÷ servings. Bulk daily cost = bag cost ÷ servings. Days to pay off = bag cost ÷ daily savings.

Scratch vs Boxed Cost Comparer: Boxed per serving = box cost ÷ servings. Scratch per serving = flour cost ÷ uses + egg cost ÷ eggs per carton.

Meatless Meal Savings Aggregator: Weekly savings = (meat cost − meatless cost) × meals per week. Annual savings = weekly savings × 52.

Thermostat Degree-Dollar Calculator: Monthly savings = base bill × 0.03 × degrees changed.

Laundromat vs Used Washer Breakeven: Savings per load = laundromat cost − home cost. Months to break even = washer price ÷ (savings per load × loads per month).

Vampire Power Drain: Monthly cost = wattage × 24 hours × 30 days ÷ 1000 × kWh rate. Sum selected devices.

Crisis & Survival Calculators

Income vs Lifestyle Runway: Monthly surplus or deficit = income − expenses. Months until broke = savings ÷ deficit. Months to 3-month emergency fund = (3 × expenses − savings) ÷ surplus.

Next Paycheck Survival Gauge: Days until payday = next payday date − today. Daily allowance = checking balance ÷ days until payday.

Bare Bones Budget Stripper: Survival total = rent + groceries + utilities + transport. Discretionary total = sum of all other expenses entered.

Payday Loan Rollover Simulator: Fee per rollover = loan amount × fee per $100 ÷ 100. Total cost = loan amount + (fee × number of rollover periods). APR = total fees ÷ loan amount × (52 ÷ rollover periods in weeks) × 100.

Emergency Skip-a-Bill Roulette: Each bill type gets a risk weight from 0 to 10. The list is sorted descending by weight.

Partial Payment Optimizer: Loop through bills. Pay = min(available cash, bill balance, $20 threshold). Subtract payment from available cash and continue.

Savings & Goal Calculators

Savings Goal Visualizer: Weeks to goal = (target − current savings) ÷ weekly savings.

Guilt-Free Fun Budget Mapper: Fun budget = monthly net income − rent − utilities − groceries − transport − debt minimums.

F-You Money Calculator: Months covered = savings ÷ monthly expenses. FIRE portfolio target = monthly expenses × 12 ÷ safe withdrawal rate.

Free Shipping Trap Calculator: Gap to free shipping = threshold − cart total. Filler scenario cost = cart + filler. Pay-shipping scenario cost = cart + shipping cost.

0% APR Ticking Time Bomb: Months until promo end = promo end date − today. Months to pay off = balance ÷ monthly payment. If the payoff months exceed the promo months, the remaining balance is hit with the post-promo APR.

Student Loan Extra $50 Visualizer: The tool amortizes the loan month by month under both payment plans. Interest = balance × monthly rate. Principal = payment − interest.

Balance Transfer Breakeven Tool: Monthly interest = balance × APR ÷ 12. Transfer fee = balance × fee %. Breakeven months = transfer fee ÷ monthly interest. When that lands inside the promo term, the tool reports a year of interest saved.

Moving Out Cost Estimator: Total = rent + deposit + first month rent + last month rent + utility setup fees. Deposit = rent × deposit multiplier.

BNPL Invisible Debt Tracker: Total monthly BNPL = sum of all entered payments. Total purchase cost = sum of all entered item costs.

Vacation Sinking Fund Planner: Weeks until departure = (departure date − today) ÷ 7 days. Weekly transfer = (trip cost − current savings) ÷ weeks.

Loan Trap & Hidden Fee Calculators

Rent-to-Own True Cost Multiplier: Total cost = weekly payment × number of weeks. Markup = total cost − retail price. Implied premium = markup ÷ retail price × 100.

Cash Advance App True APR: Fee rate = fee ÷ advance amount. APR = fee rate × (365 ÷ days until repayment) × 100.

Auto Loan Hidden Cost Revealer: Loan amount = price − down payment. Monthly payment = P × (r(1+r)^n) ÷ ((1+r)^n − 1), where r is monthly rate and n is term. Total interest = payment × n − loan amount.

Lottery / Scratch-Off Expected Value: Expected value per ticket = (average prize ÷ odds) − ticket cost. Annual burn = expected loss per ticket × tickets per week × 52.

Gambling / Sportsbook Drain Tracker: Average loss per wager = wager × average loss percentage. Weekly loss = average loss per wager × wagers per week. Annual loss = weekly loss × 52.

MLM Income Reality: Net income = (average monthly income × months active) − startup cost − (monthly cost × months active). Hourly rate = net income ÷ hours worked if you also enter hours.

Gym Ghost Membership Cost: Cost per visit = monthly fee ÷ max(actual visits, 1).

Extended Warranty True Cost: Expected claim value = claim probability × average claim cost. Expected value = expected claim value − warranty price. Break-even = warranty price ÷ claim probability.

Pawn Shop True Cost: Monthly rate = monthly APR ÷ 100. Balance after interest = loan × (1 + monthly rate)^months. Total to reclaim = balance + storage fees.

Buy-Here-Pay-Here Car Math: Lot cost = weekly payment × 104. Alternative cost = bus pass × 12 + used car price. Savings = lot cost − alternative cost.

Tax Refund Advance Trap: Advance fee = refund × fee percentage. Time value = refund × HYSA APR ÷ 365 × 14 days. True cost = advance fee − time value.

Prepaid Debit Card Fee Drain: Monthly drain = monthly fee + reloads × reload fee + ATM withdrawals × ATM fee. Annual drain = monthly drain × 12.

IRS Payment Plan vs Penalty: Do-nothing penalty = balance × 0.005 × months. Plan cost = setup fee + balance × 0.0025 × months. Savings = penalty − plan cost.

Money Visualizer Tools

Visual Sankey Diagram Generator: Total income = entered income. Each expense = entered amount. Remainder = income − total expenses.

Credit Limit Utilization Slider: Utilization = current balance ÷ credit limit × 100.

Bank & Bill Fee Calculators

Overdraft vs Late Fee Decider: If your balance covers the bill there is no fee either way. Otherwise you owe the bill under both options, so the tool compares the two fees on their own and names the cheaper one.

Collection Agency Ignore vs Pay Math: Years elapsed = today − date of first delinquency. If years elapsed ≥ statute of limitations, the debt may be time-barred.

Minimum Balance Fee Drain: Total fees = monthly fee × months. Effective annual drain = monthly fee × 12 ÷ current balance × 100.

Check Cashing Fee Visualizer: Fee = check amount × fee percentage ÷ 100. Annual cost = fee × number of checks per year.

Title Loan "Lose My Car" Countdown: Monthly interest = loan balance × monthly APR ÷ 100. New balance = previous balance + interest. Equity = car value − loan balance.

Late Fee Compounding Shocker: New balance = missed payment + late fee. Interest = new balance × penalty APR ÷ 12. Minimum payment = new balance × minimum %.

Medical Bill Settlement Target: Offer range = bill amount × 20% at the low end and × 30% at the high end, the band hospitals and collectors commonly accept to settle a bill in cash.

Grace Period Tracker: Grace days = late fee date − due date. If paid before the late fee date, you avoid the late fee but may still pay interest if you carried a balance.

Subscription Bleed Out Checker: Monthly bleed = sum of all subscription costs. Annual bleed = monthly bleed × 12.

Pay-to-Pay Fee: Annual cost = convenience fee × bills per month × 12.

Income Calculators

Gross to Net Take-Home Pay: Net pay = gross salary × (1 − total deduction rate ÷ 100). Deduction rate = federal + state + FICA + other.

Is Your Raise Actually a Raise?: Real raise = nominal raise − inflation − (nominal raise × marginal tax rate). Take-home multiplier = (1 + nominal raise) × (1 − tax rate) ÷ (1 + inflation).

Side Hustle Real Hourly Rate: Total hours = billed hours + unpaid hours. Gas cost = miles ÷ MPG × gas price. Net pay = gross pay × (1 − tax rate) − gas cost. Real hourly rate = net pay ÷ total hours.

401k Match Left on the Table: Matched contribution = min(your contribution, employer match %). Employer match = matched contribution × employer match % × salary.

Cash Under the Table vs Future Benefits: Tax saved = income × tax rate. Future benefit lost = income × 0.062 × 2 (employer and employee Social Security match). Net cost = benefit lost − tax saved.

Wage Garnishment Survival Math: Post-garnishment pay = gross paycheck × 0.75. Subtract rent, groceries, utilities, transport, and other expenses to find surplus or shortfall.

Long-Term Money Calculators

Cost of Waiting to Invest: Future value = monthly contribution × (((1 + monthly rate)^months − 1) ÷ monthly rate). The difference = later-start value − now-start value.

Recurring Habit Compounder: Total spent = habit cost × frequency × 12 × years. Future value if invested = monthly habit cost × frequency × (((1 + monthly rate)^months − 1) ÷ monthly rate).

Cash Erosion From Inflation: Future value = cash × (1 − inflation rate)^years. Lost purchasing power = cash − future value.

Early 401k / IRA Withdrawal Penalty: Traditional 401k / IRA: penalty = withdrawal × 0.10, income tax = withdrawal × tax bracket, cash received = withdrawal − penalty − tax. Roth IRA: contributions come out first, tax- and penalty-free; only earnings above your contribution basis take the 10% penalty and income tax.

Big Decision Calculators

Rent vs Buy Total Cost: Rent cost = rent × 12 × years. Buy cost = down payment + mortgage payments + taxes + insurance + maintenance − estimated home appreciation.

Car Total Cost of Ownership: Yearly gas = miles per year ÷ MPG × gas price. Insurance and maintenance are entered monthly, so each is multiplied by 12. Value left after N years = purchase price × (1 − annual depreciation rate) to the power of N, and the depreciation charge is what that erased, spread evenly across the years. Yearly cost = gas + insurance + maintenance + depreciation.

Used vs New Car Depreciation Race: New car loses about 1% per month. Used car loses about 0.5% per month. The chart plots both curves.

Lease vs Buy Auto Visualizer: Lease total = monthly lease × total months. Buy total = purchase price + maintenance × total months.

Pet Lifetime Cost Estimator: Food cost = weight × 0.05 × food price per pound × 365 × lifespan. Vet cost = annual vet risk × lifespan. Total = food + vet.

College ROI vs Debt: Annual salary premium = estimated starting salary for major − high school grad salary. Years to pay off = total debt ÷ annual premium.

Wedding Budget Reality Check: Venue/food limit = 50% of budget each. Photo limit = 12% of budget. The tool flags overspending.

Baby First Year True Cost: Total = diapers + formula + deductible + extras.

All-Inclusive Resort True Cost: Package total = advertised price per person × travelers × (1 + checkout tax % ÷ 100). Travel = (airfare + bag and seat fees + entry and exit taxes) × travelers. On-site = (tips per day + premium drinks per day) × nights. Off-resort = excursions + souvenirs, and the foreign transaction fee is off-resort × fee % ÷ 100. True total = package total + travel + ground transport + on-site + off-resort + foreign transaction fee + resort extras + travel insurance. Real cost per person per night = true total ÷ (travelers × nights).

Legal & Catastrophe Calculators

Lease-Break vs Eviction Math: Lease break cost = penalty + lost deposit. Eviction cost = future rent increase × 84 months + deposit hike.

Divorce Asset Splitter: Each party receives total asset value ÷ 2.

Co-Signing Ruin Simulator: New DTI = (existing debt + co-signed loan) ÷ gross income. If DTI > 40%, a warning appears. A missed payment subtracts a fixed 80 points from the score.

Medical Debt Charity Care Eligibility: Income percentage = (income ÷ (FPL base × household size)) × 100. Under 200% usually qualifies.

Cease & Desist Letter Generator: String template with your name, collector name, and account number inserted.

Small Claims Court ROI: Total cost = filing fee + hours off work × hourly wage. Expected return = amount owed × win probability. Net ROI = expected return − total cost.

Chapter 7 Means Test Calculator: Annual income = monthly income × 12. If annual income is below state median income for your household size, you likely pass.

Zombie Debt Identifier: Years since delinquency = (today − date of last activity) ÷ 365.25. If 7 years or more, it is likely zombie debt.

Traffic Court Plea Bargain Math: Insurance hike = ticket surcharge × 36 months. Lawyer total = lawyer fee + court costs. Hire a lawyer if insurance hike is greater.

Rent-to-Own Early Buyout Calculator: Required weekly payment = cash price ÷ 12 weeks.

Bounced Check Ripple Effect: Total damage = base bounce fee + pending transactions × NSF fee per transaction.

Credit Repair Scam vs DIY: Scam cost = monthly fee × months. DIY cost = certified mail fee × number of disputes. Savings = scam cost − DIY cost.

Cable Cutting Penalty Visualizer: Months to break even = ETF ÷ monthly savings.

Community College 2-Year Savings: University debt = university annual cost × 4. CC path debt = CC cost × 2 + university cost × 2. Savings = university debt − CC path debt.

Pawn vs Sell vs Trade Matrix: Pawn loss = item value − pawn loan + pawn fees. Sell net = marketplace price − shipping. Better option = sell if sell net > pawn loss.

Storage Unit Bleed Calculator: Months to surpass value = floor(item value ÷ monthly fee).