Calculators & converters

Online percentage calculator: calculate the percentage value, percentage rate, base value, percentage change, increases, decreases, and differences, with step-by-step calculations. Runs entirely in your browser.

Online discount calculator: calculate the price after a discount, discount percentage, original price, and 3-for-2 offers. Apply multiple discounts in sequence, add optional tax, and see the calculation steps. Runs entirely in your browser.

Convert inches to cm and cm to inches, including fractional inches, feet and inches, screen sizes, and eight units of length, with calculations. Runs entirely in your browser.

Online VAT calculator: add or remove VAT, calculate tax rates, and analyze invoices with multiple rates. Includes tax rates for 30 countries. Runs entirely in your browser.

Date and day calculator: calculate days between two dates, add or subtract days, and calculate business days and age, with steps shown. Runs entirely in your browser.

Online working hours calculator: calculate working hours with breaks, weekly hours, and overtime; add times and convert minutes to decimal hours. Runs entirely in your browser.

Convert lbs to kg and kg to lbs, plus pounds, stone, ounces, and grams. With calculation steps and tables, right in your browser.

Convert Celsius to Fahrenheit and Fahrenheit to Celsius, as well as Kelvin and Rankine. Includes step-by-step calculations, an oven temperature chart and an absolute-zero check, right in your browser.

Online hourly wage and overtime calculator: calculate overtime with premium pay, payout or time off in lieu, weekly pay with overtime, and hourly wage from monthly salary. Runs entirely in your browser.

Convert numbers to Roman numerals and back, write dates, and calculate with Roman numerals using a chart up to 3999. Runs entirely in your browser.

Convert km to miles and miles to km, plus meters, feet, yards and nautical miles. With calculations and tables for running distances and speeds, right in your browser.

Convert liters to gallons and gallons to liters, including US and UK gallons, cups, ml and fl oz. With calculations and tables, right in your browser.

Calculate electricity costs for PCs, servers, NAS devices and network equipment: enter watts, hours and electricity price, then view kWh and costs per day, month and year with calculations.

Calculate UPS requirements: apparent power in VA from watts and cos φ, a suitable UPS size with headroom, and battery runtime, with step-by-step calculations for each.

Calculate storage needs for images, audio and video: enter resolution, color depth, sample rate or bitrate, and view the size in bytes, KiB, MiB and GiB with calculations for AP1.

Online weighted decision matrix: weight criteria, rate options, view scores and rankings with calculations, and export the table for your project documentation.

Online rule of three and ratio calculator: solve proportions like 3 : 4 = 12 : x, simplify and scale ratios, and calculate direct and inverse proportions with step-by-step solutions.

Convert bytes, GB and TB (decimal and binary), and calculate download time, required bandwidth and monthly traffic, for example for a server's traffic allowance.