Distance to Horizon Calculator
Find the horizon distance from your height, with optional refraction and target visibility. Outputs surface and line-of-sight distances.
Sam Gorman
Diopter Calculator
Convert between diopters and focal length, combine two lens powers, and (optionally) estimate magnifier power with clear sign handling.
Diffraction Grating Calculator
Solve the grating equation for angle, wavelength, spacing, or line density. Includes incidence angle, sign convention, and order feasibility checks.
Lease Calculator
Estimate a car lease payment and due-at-signing with fees, taxes, and a clear breakdown that helps match a dealer quote.
Boat Loan Calculator
Estimate boat loan payment, financed amount, cash due, total interest, and payoff time with optional tax, fees, and extra payments.
Personal Loan Calculator
Estimate monthly payment, total interest, payoff date, fees, and effective APR. See how extra payments change payoff time and interest saved.
Business Loan Calculator
Estimate business loan payments, interest, fees, net proceeds, and an effective APR. Includes interest-only, balloon, extra payments, and schedule pre
Discount Calculator
Calculate final price and savings with percent or dollar discounts, stacked coupons, quantity, and optional sales tax (before or after discount).
Commission Calculator
Calculate commission for flat, tiered, or quota plans. Add splits, returns, caps, and draw. Get tier-by-tier breakdown and effective rate.
Budget Calculator
Build a simple monthly budget from take-home income, total your categories, see surplus or shortfall, and compare to 50/30/20 or custom rules.