Move a date or count an interval
Add calendar units for a future date; use Date Duration for elapsed or inclusive day counts.
Open Date CalculatorBUILT FOR EVERYDAY WORK
Calculators
Calculate dates, percentages, loan payments, savings goals, BMI, and project quantities. Free online calculators with formulas, examples, and clear assumptions.
Date Calculator
Add or subtract years, months, weeks, and days from a date. See the resulting date, weekday, and calendar-day difference.
Date Duration Calculator
Find the calendar-day difference between two dates, with weeks and a years, months, and days breakdown. Choose whether to include the end date.
BMI Calculator
Calculate adult BMI from metric or imperial height and weight. See the BMI value, adult screening category, and formula for ages 20 and above.
Square Footage Calculator
Calculate rectangular area in square feet, meters, yards, inches, and acres. Add or subtract an area and estimate cost from your own unit price.
Concrete Calculator
Estimate slab concrete volume from length, width, and depth. Add a waste allowance and optional density, bag yield, and pricing for your project.
Gravel and Stone Calculator
Estimate gravel, stone, sand, or soil volume for a rectangular area. Use your material density and price to calculate weight and cost.
Savings Goal Calculator
Find the monthly deposit needed to reach a savings goal at a fixed interest rate. Review contributions, interest, and a month-by-month balance schedule.
Loan Payment Calculator
Calculate fixed-rate loan payments with an optional down payment. Compare principal and interest totals, then review or export the repayment schedule.
Mortgage Calculator
Estimate fixed-rate mortgage payments, taxes, insurance, PMI, HOA, and financed fees. See the payment breakdown, loan-to-value ratio, and amortization schedule.
BC & AD Date Calculator
Measure the interval between BCE and CE dates using an explicit Gregorian or Julian calendar. Compare calendar days, weeks, years, and months across eras.
Percentage Calculator
Find percentages and changes, apply a discount or increase, and work backward from a part to its total.
11 useful tools. Free to use, with no signup.
Choose the right tool for your task
Match the model to the question before entering numbers. A calendar month is not 30 fixed days, a material volume is not a weight, and a loan payment is not a complete ownership budget.
Estimate a repayment schedule
State the nominal rate, financed principal, term, and payment frequency before comparing totals.
Open Loan Payment CalculatorEstimate materials from dimensions
Begin with area, then include depth for volume and supplier density for a weight estimate.
Open Square Footage CalculatorMethods and worked examples
Calendar days, date differences, and month-end arithmetic
Reproduce leap-year and month-end examples, choose inclusive or elapsed day counts, and understand why one calendar month is not always 30 days.
Read the guidePercentages, discounts, and percentage points
Choose the right denominator, calculate a final discounted price, and distinguish a change in a rate from its relative percentage change.
Read the guideFrom floor area to material volume and weight
Work from measured dimensions to net area, layer volume, allowance, supplier density, whole bags, and a price with the correct billing unit.
Read the guideRead savings, loan, and mortgage estimates correctly
Reproduce fixed-rate examples, understand cent adjustments in schedules, and separate a loan payment from fees and recurring ownership costs.
Read the guideAdult BMI, height units, and category boundaries
Convert mixed feet and inches correctly, reproduce an adult BMI calculation, and understand why a rounded result does not determine its screening category.
Read the guide