Home Affordability Calculator
Last reviewed 25 August 2026
Added a downloadable Excel/CSV workbook generated from your inputs.
Barista FIRE Calculator
Last reviewed 25 August 2026
Published with the Barista FIRE formula (spending gap after part-time income, divided by the safe withdrawal rate), a full-FIRE comparison, a gap-to-Barista-FIRE comparison against your current invested amount, a hand-verified worked example, sources (Corporate Finance Institute on the four percent rule; SEC Investor.gov on diversification), and an FAQ.
Gravel Calculator
Last reviewed 25 August 2026
Third calculator in the DIY & Materials category.
Sales Tax Calculator
Last reviewed 23 August 2026
Published with the formula, state rate table, a worked example, and an FAQ.
Consumer Surplus Calculator
Last reviewed 18 August 2026
Reviewed the formula and assumptions for accuracy.
Producer Surplus Calculator
Last reviewed 18 August 2026
Reviewed the formula and assumptions for accuracy.
Deadweight Loss Calculator
Last reviewed 18 August 2026
Reviewed the formula and assumptions for accuracy.
Gratuity Calculator
Last reviewed 16 August 2026
Published the India gratuity calculator with the 15/26 formula, per-year accrual, and Payment of Gratuity Act 1972 sourcing.
UAE Gratuity Calculator
Last reviewed 16 August 2026
Published the UAE end-of-service gratuity calculator with the 21/30-day formula, statutory 2-year cap, and Federal Decree-Law No. 33 of 2021 sourcing.
Freelancer vs Employee Calculator
Last reviewed 16 August 2026
Published the freelancer-vs-employee rate calculator: required freelance hourly/day rate to match a target salary, accounting for business expenses, lost benefits, self-employment tax, and realistic billable hours.
Real Estate Investment Calculator
Last reviewed 16 August 2026
Published the real estate investment calculator: total ROI, annualized return, cash-on-cash, and equity build-up from cash flow, principal paydown, and appreciation.
Grade Calculator
Last reviewed 16 August 2026
Cross-linked with the new GPA Calculator once it shipped.
GPA Calculator
Last reviewed 16 August 2026
Credit-hour-weighted GPA from letter grades or percentages, with an optional cumulative-GPA merge.
Tip Calculator
Last reviewed 16 August 2026
Published the tip calculator with bill amount, tip percentage, and per-person split.
Comparative Advantage Calculator
Last reviewed 16 August 2026
Published the comparative advantage calculator: comparative and absolute advantage between two producers and two goods, plus the gains-from-trade range.
Bicycle Tire Pressure Calculator
Last reviewed 16 August 2026
Launched as the first calculator in the new Everyday category.
Concrete Calculator
Last reviewed 16 August 2026
Launched as the first calculator in the new DIY & Materials category.
Paint Calculator
Last reviewed 16 August 2026
Second calculator in the DIY & Materials category.
Rent vs Buy Calculator
Last reviewed 15 August 2026
Published the rent-vs-buy calculator: compares buying a home to renting and investing the difference, showing which builds more wealth and the year buying breaks even.
Car Lease vs Buy Calculator
Last reviewed 15 August 2026
Published the car lease-vs-buy calculator: compares the monthly payment, ending equity if you buy, and invested savings if you lease, over the same years.
Debt Consolidation Calculator
Last reviewed 15 August 2026
Published the debt consolidation calculator: compares a consolidation loan's monthly payment, payoff time, and total interest against paying existing debts separately.
Debt Payoff vs Investing Calculator
Last reviewed 15 August 2026
Published the debt-payoff-vs-investing calculator: compares ending net worth from paying off debt versus investing the same cash over the same years.
Days Calculator
Last reviewed 7 August 2026
Corrected taxonomy: moved from Math & Statistics to Time & Date, which better matches how people actually use it, and updated the address from /math/days-calculator/ to /time-date/days-calculator/. The old link still works.
Global Import Duty Calculator
Last reviewed 6 August 2026
Added as the Tax category's fourth tool alongside the Income Tax, VAT/GST, and Salary & Take-Home Pay calculators.
DDP vs DAP Cost Calculator
Last reviewed 6 August 2026
Added as the Business & Ecommerce category's ninth tool alongside Profit Margin, Markup, Break-Even, Ecommerce Profit, Break-Even ROAS, LTV:CAC, Price Elasticity of Demand, and AI Agent Cost calculators.
Roofing Calculator
Last reviewed 6 August 2026
Added as the Home & Energy category's fourth tool alongside the Solar Panel Roof-Fit Calculator, the Gutter Calculator, and the Insulation Calculator.
Decking Calculator
Last reviewed 6 August 2026
Added as the Home & Energy category's fifth tool alongside the Solar Panel Roof-Fit Calculator, the Gutter Calculator, the Insulation Calculator, and the Roofing Calculator.
Fence Calculator
Last reviewed 6 August 2026
Added as the Home & Energy category's sixth tool alongside the Solar Panel Roof-Fit Calculator, the Gutter Calculator, the Insulation Calculator, the Roofing Calculator, and the Decking Calculator.
Timesheet Calculator
Last reviewed 5 August 2026
Added as the Time & Date category's next tool alongside the Time Zone Converter.
Age Calculator
Last reviewed 5 August 2026
Added as the Time & Date category's next tool.
Time Percentage Calculator
Last reviewed 5 August 2026
Added as the Time & Date category's next tool alongside the Time Zone Converter.
Solar Panel Roof-Fit Calculator
Last reviewed 5 August 2026
Launched Calculator Matters' Home & Energy category with this calculator as its first tool.
Gutter Calculator
Last reviewed 5 August 2026
Added as the Home & Energy category's second tool alongside the Solar Panel Roof-Fit Calculator.
Insulation Calculator
Last reviewed 5 August 2026
Added as the Home & Energy category's third tool alongside the Solar Panel Roof-Fit Calculator and the Gutter Calculator.