Free Online Calculators
& Unit Converters
Fast, accurate tools — no signup needed
ComputeZap offers free online calculators and unit converters for finance, math, cooking, and everyday use. Every tool works instantly in your browser — no downloads, no account required. Whether you need to calculate CD interest, convert liters to gallons, find a sale price, or measure square footage, we have a fast and accurate tool for it.
Finance Calculators
CD Calculator
Calculate Certificate of Deposit earnings with compound interest
High Yield🏠Mortgage Payoff Calculator
See how early payments reduce your mortgage term and interest
🧾Reverse Sales Tax Calculator
Find original price before tax from the final amount paid
Easy❄️Debt Snowball Calculator
Pay off debt faster — see payoff order, interest saved, and debt-free date
PopularDate & Time Tools
Days From Today Calculator
Find the exact date any number of days from today — 30, 60, 90 days and more
Popular🗓️30 Days From Today
What date is exactly 30 days from today? Net 30 payment deadline calculator
📆90 Days From Today
Find the date 90 days (3 months / one quarter) from today's date
Math Calculators
Percent Off Calculator
Calculate discounted price — great for shopping deals
Popular📐Pythagorean Theorem Calculator
Find any side of a right triangle using a² + b² = c²
⏱️Time to Decimal Calculator
Convert hours & minutes to decimal format for timesheets
FastUnit Converters
Square Footage Calculator
Calculate area in sq ft for rooms, land, or any space
⚖️kg to lbs Converter
Convert kilograms to pounds instantly
📐cm to inches Converter
Convert centimeters to inches — most searched converter
🌡️Celsius to Fahrenheit
Temperature conversion — °C to °F formula applied instantly
🚤Knots to MPH Converter
Convert nautical speed — knots to miles per hour
🥛Cups to Gallons Converter
Kitchen & cooking volume conversion
🥄Cups to Tablespoons
How many tablespoons in a cup? 1 cup = 16 tbsp — all fractions covered
New🪣Liters to Gallons
Convert liters to US or Imperial gallons instantly. 1 gallon = 3.785 liters
NewHow Our Tools Help You
Finance Calculators — Make Smarter Money Decisions
Our finance calculators handle the math so you can focus on the decision. The CD calculator computes exact interest earnings using the compound interest formula — enter your principal, APY, and term to see your final balance. The mortgage payoff calculator shows how much interest you save by making extra payments each month. The reverse sales tax calculator works backwards from a receipt total to find the original pre-tax price, which is useful for expense reports, business accounting, and budgeting.
Days From Today Calculator — Track Dates & Deadlines
Knowing the exact date that falls 30, 60, or 90 days from today matters for contracts, invoices, and project planning. Our days from today calculator works for any number of days — just enter a number and get the future date instantly. Use 30 days from today for net-30 payment terms, 60 days for supplier lead times, and 90 days from today for quarterly reviews and filing deadlines. All calculations account for the correct calendar date including month lengths and leap years.
Unit Converters — Cooking, Science & Everyday Measurements
Unit conversion should be fast and error-free. Our cups to tablespoons converter covers every fraction — ¼ cup, ⅓ cup, ½ cup, and 1 cup equals exactly 16 tablespoons. The liters to gallons converter supports both US gallons (1 gallon = 3.785 liters) and Imperial UK gallons (1 gallon = 4.546 liters). Whether you are scaling a recipe, converting fuel economy, or working with international measurements, our converters deliver accurate results instantly with no rounding errors.