Calculators

Choosing the right calculator

Calculators on FreeMicroTools are for the numbers that come up on a job, at a desk or around a table. For building and the yard, the Roof Pitch, Concrete, Deck Material and Square Footage calculators cover pitch, concrete bags, boards and floor area; the Paint Calculator gives the gallons for a room or a whole house, and the Gravel Calculator the cubic yards, tons and bags of gravel, soil or mulch. The Unit Converter turns metric into US units and back with exact factors.

For work and money, the Hours Calculator totals a time card, Salary to Hourly turns pay into every pay period, and the Tip and Percentage calculators handle everyday sums. The Mortgage Calculator gives the full monthly payment with taxes and PMI, the Sales Tax Calculator adds or removes US sales tax for any state, the Inflation Calculator shows what old dollars are worth today, and the EMI, SIP, Compound Interest and GST calculators cover loans, savings and Indian tax.

For school, dates and clocks, the GPA and Grade calculators work out grade point averages, class grades and the score needed on a final, and the Fraction and Average calculators show every step, from mixed numbers to standard deviation. The Date Difference, Age and Due Date calculators count days, years and weeks of pregnancy, Countdown to a Date counts down to any holiday, while the Time Zone and Military Time converters and the Online Stopwatch and Timer handle the clock. The BMI and Calorie calculators give screening figures and daily calories from published formulas, the Pace Calculator gives running pace and race times, and the Scientific Calculator handles the rest.

Everything you type stays in your browser. Rules differ by place and person, so check the official source before you order, build, pay or decide.

Questions

How do I work out roof pitch?

Hold a level flat against the roof or a rafter, measure 12 inches along it and measure straight down to the roof surface: that measurement is the rise per 12 inches of run, written as rise:12. The Roof Pitch Calculator converts it to degrees and percent, and works out rafter length and roof area from it.

How many bags of concrete do I need for a slab?

Multiply the slab's length, width and thickness to get the volume, then divide by the yield printed on the bag. The Concrete Calculator does this for a slab, footing, column, wall or steps, in cubic yards or cubic metres, and shows the count for 40, 50, 60 and 80 lb bags and 20, 25 and 40 kg bags, with a margin for waste.

How are overtime hours worked out?

Under the US Fair Labor Standards Act, non-exempt employees earn at least one and a half times their regular rate for hours over 40 in a workweek. Some states also pay daily overtime. The Hours Calculator adds up the week, takes off breaks, and splits the hours at the weekly and optional daily limits you set.

Are these calculators free?

Yes. Every calculator is free, with no sign-up, and the numbers you type are worked out in your browser and never sent to us.