Solvers

What each Solver does, how to use it, and the everyday math behind it.

• What Are Solvers?Solvers are small formula calculators inside coolca.lc for tips, tax, discounts, loans, markup, unit conversions and more. Fill in what you know, and the Solver works out the rest, in any direction.
• How Much to TipHow much to tip in the US at restaurants, buffets, bars, delivery, salons and hotels, with a tip chart, the math to do it in your head, and a free tip calculator.
• How to Split a BillThe fair ways to split a restaurant bill or shared expense: evenly, by what each person ordered, or by share, with the tip and tax handled correctly. Includes a free split bill calculator.
• How to Calculate Sales TaxHow to add sales tax to a price, take tax back out of a total the right way, and find the tax rate from a receipt, with formulas, worked examples and a free sales tax calculator.
• How to Calculate a DiscountHow to work out a sale price from a percentage off, find the original price from a sale price, find the percent off, and handle stacked discounts and coupons, with a free discount calculator.
• Markup vs MarginMarkup is profit as a percentage of cost; margin is profit as a percentage of the selling price. Learn the formulas, convert between them, avoid the classic pricing mistake, and use free markup and margin calculators.
• How Loan Payments Are CalculatedHow a monthly loan payment is worked out, why early payments are mostly interest, how the rate and the term change what you pay, and how much you can borrow for a given payment, with a free loan calculator.
• How to Calculate Percent ChangeThe percent change formula, worked examples of increases and decreases, why a 50% drop needs a 100% gain to recover, percent versus percentage points, and a free percent change calculator.