Online Calculators
A collection of free online calculators for everyday math and projects: percentages and date differences, home-renovation estimates for paint, tile, concrete and wallpaper, plus ring and watch sizing.
Calculator
Basic and scientific modes, voice readout in 9 languages, large buttons and a running paper-tape — built to be easy for seniors, children and everyone else.
Percentage Calculator
Percent of a number, percent change, discount, tip, VAT, markup
Date Difference Calculator
Days between two dates, business days and holidays
Ring Size Calculator
Pick a method below. Everything runs in your browser.
Watch Size Calculator
Wrist → ideal case diameter, lug-to-lug, strap width
BAC Calculator
tools/bac-calculator.hint
Julian ↔ Gregorian
tools/julian-gregorian-converter.hint
Stair Calculator
Enter the floor-to-floor height and get the riser height, tread depth, stair angle and stringer length, with comfort and code checks.
Tile Calculator
Enter the room size and the tile size, add a waste margin, and get the number of tiles and boxes to buy.
Paint Calculator
Enter the room size, the number of coats and the paint coverage, and get the litres or gallons to buy.
Wallpaper Calculator
Enter the room size, the roll size and the pattern repeat, and get the number of rolls to buy.
Concrete Calculator
Enter the dimensions of a slab, footing or round column and get the concrete volume and the number of pre-mix bags.
Lumber Calculator
Enter the board thickness, width, length and quantity to get the board feet per board, the total and the cost.
Fence Calculator
Enter the fence length and post spacing to get the posts, sections, rails and pickets you need.
Running Pace Calculator
Enter a distance and the time it took to get your pace, speed and predicted race finish times.
Depth of Field Calculator
Set your sensor, focal length, aperture and focus distance to see the depth of field and focus limits.
ND Filter Calculator
Pick the exposure without a filter and the ND filter you are using to get the corrected shutter speed.
Print Size Calculator
Enter the image pixel dimensions to find the print size at a chosen DPI, or the DPI at a target size.
Clothing Size Converter
Pick a category and your size in one region to see the matching size everywhere else.
