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Grouped by category. Every tool cites its formula and passes published test cases before it ships.

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Money & Finance

Cosigner Loan Risk CalculatorSee the monthly payment you'd be liable for, your before-and-after debt-to-income ratio, and the mortgage buying power you'd give up — before you co-sign.
Medical Bill Payment Plan CalculatorCompare a 0% hospital plan, a deferred-interest medical credit card, and a personal loan — including the retroactive interest charge if you miss the promo.
Home Insurance Increase CalculatorEnter your renewal history to see your premium's real growth rate vs. inflation, the extra dollars you've paid, and whether it's time to get quotes.
Airbnb Host Insurance Gap CalculatorSee the dollar gaps between your homeowner's policy, Airbnb's AirCover, and a dedicated STR policy across four real claim scenarios.
Airbnb Profit CalculatorMonth-by-month seasonal cash flow for short-term rentals — peak profits, off-season losses, and the cash buffer you need, not a flat vacancy rate.
Home Inventory CalculatorBuild a room-by-room inventory that stays on your device, and see which categories blow past your policy's special limits before you need to claim.
Auto Loan Cosigner CalculatorA car loses value faster than the loan shrinks. See the months you'd be underwater — and what you'd owe after a repossession sale.
Cosigner Release CalculatorTrack your progress toward release — and weigh it against refinancing, given that a 2015 CFPB review found ~90% of release applications on private student loans were rejected.
Deferred Interest CalculatorWhat a "no interest if paid in full" promo really costs if you miss it — the interest charged back to day one, and the reduced-APR plan that's often cheaper.

Health & Fitness

First tools in this category are being built and verified now.

Converters & Scalers

Adding Machine CalculatorA running tape you can read back: every step stays on screen, so you can check the work and copy it — not just the answer.

Planners & Generators

First tools in this category are being built and verified now.

Tools by Profession

First tools in this category are being built and verified now.