Public proof
Public calculation tests
Selected reference cases make calculator behavior inspectable. Each case is machine-verified during the release test suite and shows the model, inputs, expected result, and tolerance.
Reference cases
| Tool | Model | Inputs | Expected | Tolerance |
|---|---|---|---|---|
| percentage-calc | X percent of Y = (X / 100) × Y | {"mode":"of","val1":15,"val2":200} | {"result":30} | ±0.000001 |
| percentage-calc | Percent change = ((new - old) / old) × 100 | {"mode":"change","val1":100,"val2":125} | {"percent_change":25} | ±0.000001 percentage points |
| debt-payoff | Single balance, monthly interest, fixed payment plus extra | {"balance":1000,"apr":12,"payment":100,"extra":50} | {"payoff_months":7,"base_payoff_months":11,"interest_saved_positive":true} | Exact months; currency ±$0.01 |
| debt-payoff | Single balance at zero APR with fixed payment | {"balance":1200,"apr":0,"payment":100,"extra":0} | {"payoff_months":12,"total_interest":0} | Exact months; currency ±$0.01 |
| bmi-calc | BMI = kilograms / meters² | {"weight":170,"heightFt":5,"heightIn":9} | {"bmi":25.1,"category":"Overweight"} | ±0.1 BMI unit |
| bmi-calc | BMI = kilograms / meters² | {"weight":120,"heightFt":5,"heightIn":4} | {"bmi":20.6,"category":"Normal"} | ±0.1 BMI unit |
| electricity-cost-calculator | kWh = watts / 1000 × hours × days; cost = kWh × tariff | {"watts":1000,"hours":2,"days":30,"rate":0.15} | {"monthly_kwh":60,"monthly_cost":9} | Energy ±0.01 kWh; currency ±$0.01 |
| electricity-cost-calculator | kWh = watts / 1000 × hours × days; cost = kWh × tariff | {"watts":60,"hours":5,"days":30,"rate":0.25} | {"monthly_kwh":9,"monthly_cost":2.25} | Energy ±0.01 kWh; currency ±$0.01 |
| tip-bill-split-calculator | Tip on subtotal; equal split | {"subtotal":100,"tax":8,"tipPct":20,"people":4,"tipOnTax":false,"roundMode":"none"} | {"tip":20,"total":128,"perPerson":32} | Currency ±$0.01 |
| tip-bill-split-calculator | Equal split rounded upward per person | {"subtotal":50,"tax":0,"tipPct":15,"people":3,"tipOnTax":false,"roundMode":"up-dollar"} | {"unroundedTotal":57.5,"total":60,"perPerson":20} | Currency ±$0.01 |
| date-calculator-workspace | UTC date-only signed difference with both boundaries counted | {"mode":"difference","startDate":"2024-02-28","endDate":"2024-03-01","inclusive":true,"excludeWeekends":true} | {"totalDays":3,"weekdayDays":3} | Exact calendar days |
| date-calculator-workspace | Add one calendar month with month-end preservation | {"mode":"add","baseDate":"2024-01-31","direction":"add","years":0,"months":1,"weeks":0,"days":0,"preserveLastDay":true} | {"resultDate":"2024-02-29","weekday":"Thursday"} | Exact date |
| discount-percent-off-calculator | Sequential percentage discounts, then fixed coupon, then tax | {"originalPrice":200,"discount1":20,"discount2":10,"coupon":5,"taxPct":8} | {"preTaxFinal":139,"discountAmount":61,"checkoutTotal":150.12} | Currency ±$0.01 |
| discount-percent-off-calculator | Fixed coupon after percentage discounts with zero floor | {"originalPrice":25,"discount1":0,"discount2":0,"coupon":40,"taxPct":10} | {"preTaxFinal":0,"discountAmount":25,"checkoutTotal":0} | Currency ±$0.01 |
| fuel-trip-cost-calculator | Miles divided by MPG; round trip and repeated trips | {"unit":"mpg","distance":120,"roundTrip":true,"efficiency":30,"fuelPrice":3.5,"travelers":4,"trips":2} | {"totalDistance":480,"fuelUsed":16,"totalCost":56,"costPerTraveler":14} | Distance/fuel ±0.000001; currency ±$0.01 |
| fuel-trip-cost-calculator | Kilometers multiplied by L/100 km divided by 100 | {"unit":"l100km","distance":300,"roundTrip":false,"efficiency":7.5,"fuelPrice":1.7,"travelers":3,"trips":1} | {"fuelUsed":22.5,"totalCost":38.25,"costPerTraveler":12.75} | Fuel ±0.000001 L; currency ±$0.01 |
| commission-calculator | Flat commission rate on all gross sales | {"mode":"flat","sales":50000,"flatRate":5} | {"commission":2500,"effectiveRate":5} | Currency ±$0.01; rate ±0.000001 percentage points |
| commission-calculator | Progressive commission brackets | {"mode":"tiered","sales":40000,"tier1Limit":10000,"tier1Rate":3,"tier2Limit":25000,"tier2Rate":5,"tier3Rate":7} | {"commission":2100,"effectiveRate":5.25} | Currency ±$0.01; rate ±0.000001 percentage points |
| debt-to-income-ratio-calculator | Front-end and back-end required-debt ratios | {"grossMonthlyIncome":8000,"housingPayment":1800,"carPayment":400,"studentLoans":100,"creditCards":50,"otherDebt":50,"targetDti":36} | {"frontEndDti":22.5,"backEndDti":30,"remainingCapacity":480} | Ratios ±0.000001 percentage points; currency ±$0.01 |
| debt-to-income-ratio-calculator | Required debt above selected planning threshold | {"grossMonthlyIncome":5000,"housingPayment":1800,"carPayment":500,"studentLoans":200,"creditCards":100,"otherDebt":0,"targetDti":36} | {"backEndDti":52,"remainingCapacity":-800,"withinTarget":false} | Ratios ±0.000001 percentage points; currency ±$0.01 |
| down-payment-calculator | Percentage down payment plus percentage closing costs | {"homePrice":400000,"mode":"percent","downPercent":20,"downAmount":0,"closingCostPercent":3,"availableCash":100000} | {"downPayment":80000,"loanAmount":320000,"ltv":80,"cashToClose":92000,"cashRemaining":8000} | Currency ±$0.01; LTV ±0.000001 percentage points |
| down-payment-calculator | Fixed down payment plus percentage closing costs | {"homePrice":250000,"mode":"amount","downPercent":0,"downAmount":50000,"closingCostPercent":2,"availableCash":70000} | {"downPayment":50000,"loanAmount":200000,"closingCosts":5000,"cashToClose":55000} | Currency ±$0.01 |
| 401k-employer-match-calculator | Simple employer percentage match up to salary-percentage limit | {"annualSalary":80000,"employeePercent":6,"employerMatchPercent":50,"matchLimitPercent":6,"payPeriods":26} | {"employeeAnnual":4800,"employerAnnual":2400,"totalAnnual":7200,"unclaimedMatch":0} | Currency ±$0.01 |
| 401k-employer-match-calculator | Employee contribution below modeled match limit | {"annualSalary":80000,"employeePercent":3,"employerMatchPercent":50,"matchLimitPercent":6,"payPeriods":26} | {"employeeAnnual":2400,"employerAnnual":1200,"maximumEmployerMatch":2400,"unclaimedMatch":1200} | Currency ±$0.01 |
| rent-vs-buy-calculator | Buyer equity versus renter investment portfolio | {"homePrice":400000,"downPercent":20,"mortgageRate":6.5,"mortgageTerm":30,"years":7,"buyClosingPercent":3,"sellCostPercent":6,"propertyTaxPercent":1.2,"annualInsurance":1800,"maintenancePercent":1,"appreciationPercent":3,"monthlyRent":2200,"rentIncreasePercent":3,"annualRenterInsurance":240,"investmentReturnPercent":5} | {"buyerEquity":173100.59009255463,"renterPortfolio":187585.86781217443,"wealthAdvantage":-14485.2777196198} | Currency ±$0.01 |
| rent-vs-buy-calculator | Short-horizon buyer equity versus renter portfolio | {"homePrice":400000,"downPercent":20,"mortgageRate":6.5,"mortgageTerm":30,"years":3,"buyClosingPercent":3,"sellCostPercent":6,"propertyTaxPercent":1.2,"annualInsurance":1800,"maintenancePercent":1,"appreciationPercent":3,"monthlyRent":2200,"rentIncreasePercent":3,"annualRenterInsurance":240,"investmentReturnPercent":5} | {"buyerEquity":102330.17790586711,"renterPortfolio":132243.2383420157,"wealthAdvantage":-29913.060436148604} | Currency ±$0.01 |
| apr-effective-interest-calculator | Fee-adjusted fixed-payment loan APR | {"amount":10000,"nominalRate":8,"termMonths":36,"fees":300,"financeFees":false} | {"monthlyPayment":313.3636546143113,"estimatedApr":10.081642376496596,"effectiveAnnualRate":10.560785961866582,"totalFinanceCost":1581.0915661152067} | Currency ±$0.01; rates ±0.000001 percentage points |
| apr-effective-interest-calculator | Fixed-payment loan with no fees | {"amount":10000,"nominalRate":8,"termMonths":36,"fees":0,"financeFees":false} | {"estimatedApr":8.000000000000705,"effectiveAnnualRate":8.299950680751845,"totalFinanceCost":1281.0915661152067} | Currency ±$0.01; rates ±0.000001 percentage points |
| inflation-impact-calculator | Constant compound inflation scenario | {"amount":1000,"inflationRate":3,"years":10} | {"futureCost":1343.916379344122,"purchasingPower":744.0939148967249} | Currency ±$0.01 |
| inflation-impact-calculator | Zero-inflation identity | {"amount":500,"inflationRate":0,"years":20} | {"futureCost":500,"purchasingPower":500} | Exact |
| bmr-tdee-calculator | Mifflin–St Jeor adult equation | {"sex":"male","age":30,"weightKg":80,"heightCm":180,"activity":1.2} | {"bmr":1780,"tdee":2136} | ±0.01 kcal/day |
| bmr-tdee-calculator | Mifflin–St Jeor adult equation | {"sex":"female","age":30,"weightKg":60,"heightCm":165,"activity":1.55} | {"bmr":1320.25,"tdee":2046.3875} | ±0.01 kcal/day |
| break-even-units-calculator | Whole-unit contribution break-even | {"fixedCosts":10000,"pricePerUnit":50,"variableCostPerUnit":30,"targetProfit":0} | {"contributionMargin":20,"breakEvenUnits":500,"requiredRevenue":25000} | Currency ±$0.01; units exact |
| break-even-units-calculator | Whole units required for target profit | {"fixedCosts":10000,"pricePerUnit":50,"variableCostPerUnit":30,"targetProfit":5000} | {"contributionMargin":20,"breakEvenUnits":750,"requiredRevenue":37500} | Currency ±$0.01; units exact |
| cash-flow-runway-calculator | Constant monthly cash burn | {"startingCash":10000,"monthlyRevenue":2000,"monthlyExpenses":3000,"revenueGrowthPct":0,"expenseGrowthPct":0,"maxMonths":24} | {"depletionMonth":10,"endingCash":0} | Month exact; currency ±$0.01 |
| cash-flow-runway-calculator | Revenue equals expenses | {"startingCash":10000,"monthlyRevenue":3000,"monthlyExpenses":3000,"revenueGrowthPct":0,"expenseGrowthPct":0,"maxMonths":12} | {"depletionMonth":null,"breakEvenMonth":1,"endingCash":10000} | Exact |
| price-increase-impact-calculator | Contribution after price and volume change | {"currentPrice":50,"newPrice":60,"currentUnits":1000,"volumeChangePct":-10,"variableCost":30} | {"currentContribution":20000,"newContribution":27000,"contributionDelta":7000} | Currency ±$0.01 |
| price-increase-impact-calculator | No price or volume change | {"currentPrice":50,"newPrice":50,"currentUnits":100,"volumeChangePct":0,"variableCost":20} | {"contributionDelta":0,"allowableDemandLossPct":0} | Exact |
| macro-planning-calculator | 4-4-9 macro allocation arithmetic | {"adultConfirmed":true,"dailyCalories":2400,"weightKg":80,"proteinPerKg":1.6,"fatPercent":30} | {"proteinGrams":128,"fatGrams":80,"carbGrams":292} | ±0.01 gram |
| macro-planning-calculator | 4-4-9 macro allocation arithmetic | {"adultConfirmed":true,"dailyCalories":1800,"weightKg":70,"proteinPerKg":1,"fatPercent":30} | {"proteinGrams":70,"fatGrams":60,"carbGrams":245} | ±0.01 gram |
| customer-lifetime-value-calculator | Constant-churn gross-contribution LTV | {"averageOrderValue":50,"purchasesPerYear":4,"grossMarginPct":60,"annualChurnPct":20,"targetLtvCacRatio":3} | {"annualGrossContribution":120,"lifetimeValue":600,"maxPlanningCac":200} | Currency ±$0.01 |
| customer-lifetime-value-calculator | Constant-churn gross-contribution LTV | {"averageOrderValue":100,"purchasesPerYear":1,"grossMarginPct":100,"annualChurnPct":50,"targetLtvCacRatio":2} | {"customerLifetimeYears":2,"lifetimeValue":200,"maxPlanningCac":100} | ±0.01 |
| subscription-churn-impact-calculator | Constant monthly churn model | {"startingCustomers":1000,"monthlyChurnPct":5,"newCustomersPerMonth":0,"arpu":20,"months":12} | {"endingCustomers":540.3600876626365,"totalChurned":459.6399123373635} | ±0.01 customer |
| subscription-churn-impact-calculator | Constant monthly churn and replacement | {"startingCustomers":1000,"monthlyChurnPct":5,"newCustomersPerMonth":50,"arpu":20,"months":12} | {"endingCustomers":1000,"finalMonthlyRevenue":20000,"requiredNewCustomers":50} | ±0.01 |
| inventory-reorder-point-calculator | Lead-time demand plus safety stock | {"averageDailySales":10,"leadTimeDays":7,"safetyStockUnits":20,"currentStockUnits":100} | {"leadTimeDemand":70,"reorderPoint":90,"orderNow":false} | ±0.01 unit |
| inventory-reorder-point-calculator | Lead-time demand plus safety stock | {"averageDailySales":5,"leadTimeDays":14,"safetyStockUnits":30,"currentStockUnits":80} | {"leadTimeDemand":70,"reorderPoint":100,"orderNow":true} | ±0.01 unit |