Calculators— Guides & Articles

• How to Calculate Week Number Based on Date in Excel

  Published 2026-08-27

  Get the ISO 8601 or US week number from any Excel date using ISOWEEKNUM or WEEKNUM, and verify results with a free Week Number Calculator.

  

• How to Calculate Ball Surface Area from Radius

  Published 2026-08-25

  Learn the 4πr² formula for ball surface area, enter a radius in your chosen unit, and read the result in the matching squared unit.

  

• How to Calculate Paint Needed for Exterior Walls

  Published 2026-08-23

  Figure out how much exterior paint to buy using wall area, coverage, coats and openings. Step-by-step guide with a worked example using a free calculator.

  

• How to Convert Power Windows to Manual: Motor Power Math

  Published 2026-08-23

  Converting power windows to manual? Calculate motor wattage and equivalent manual effort with the free Power Converter. Watts, kW, hp, BTU/h in one click.

  

• Digits of Pi Chart: Read Any Length, Grouped and Copyable

  Published 2026-08-23

  A digits of pi chart shows pi's decimal expansion grouped for easy reading. Get 100, 1,000 or 10,000 exact digits of pi, copy them, and check any position.

  

• Minimum Spanning Tree Calculator Online — Find V−1 Edges

  Published 2026-08-23

  Use an online minimum spanning tree calculator to find the lightest V−1 undirected edges from your edge list. Kruskal selection runs entirely in your browser.

  

• How to Calculate Percentage Increase Between Two Numbers

  Published 2026-08-22

  Calculate percentage increase between two numbers with the formula (new − old) ÷ old × 100. See a worked example, plus a free tool that does the math as you…

  

• How to Find Parallelogram Area and Perimeter

  Published 2026-08-22

  Find parallelogram area (A = b·h or A = a·b·sin θ) and perimeter 2(a + b) instantly. Pick a method, type your numbers, and read the result.

  

• How to Calculate Ovulation and Fertile Window

  Published 2026-08-22

  Calculate your ovulation day and fertile window using the calendar method. Step-by-step guide with a worked example, a tracking-method comparison, and tips…

  

• How to Convert Number Bases Using an Online Calculator

  Published 2026-08-22

  Convert number bases using a calculator: binary to decimal, hex to decimal, decimal to binary, and any base 2–36. Step-by-step workflow inside.