Calculators that show their work.
Dayob is a growing collection of free calculators for building projects, school, science, fitness tests and personal finance. Every tool explains the formula behind the answer, links to official sources, and runs right in your browser with no sign-up.
Construction & Landscaping
See allCubic Yard CalculatorTurn the length, width and depth of any bed, trench or hole into cubic yards, then price the order before you call the supplier.Gravel CalculatorWork out the volume, weight and cost of gravel for a driveway, path, patio or drainage trench, with densities for the most common stone types.Square Footage CalculatorAdd up the area of one room or a whole floor plan, subtract what you will not cover, and see the result in square feet, square meters and square yards.Concrete CalculatorEstimate how much concrete to order for a slab, footing, post hole or set of steps, and how many premixed bags that would take.
Math
See allRatio CalculatorSimplify any ratio, find a missing term, scale a recipe or mix, or divide an amount in a given ratio, with the working shown.Proportion CalculatorSolve a/b = c/d for any missing value with cross multiplication, and check whether two ratios are really in proportion.GCF CalculatorEnter two or more whole numbers to get their greatest common factor, least common multiple, prime factorizations and the Euclidean algorithm worked out.
School & Test Scores
See allAP Lang Score CalculatorEnter your multiple-choice result and your three essay scores to estimate your AP English Language and Composition score on the 1–5 scale.APUSH Score CalculatorPlug in your multiple-choice, short-answer, DBQ and LEQ results to estimate your AP United States History score from 1 to 5.Final Grade CalculatorFind out exactly what you need on the final exam to finish with the grade you want, and see the score needed for every letter grade.
Science
See allFitness & Assessment
See allUSMC PFT CalculatorScore your Marine Corps Physical Fitness Test by age group and sex, with event points, total score, class and pass or fail.Chronological Age CalculatorGet a child's exact age on the test date in years, months and days, the way assessment manuals calculate it, plus corrected age for babies born early.
Personal Finance
See allLatest guides
All guides
How Big Is a Cubic Yard? A Visual Guide for Ordering Bulk MaterialsA cubic yard is 27 cubic feet, a cube 3 feet on each side. Here is how to picture it, what it weighs, and how far it spreads.
Cubic Feet to Cubic Yards: The Conversion, a Chart and Common MistakesDivide cubic feet by 27 to get cubic yards. This guide shows why, gives a quick chart, and covers the inch and square-foot mix-ups that cause bad orders.
How Much Mulch Do I Need? Depth, Coverage and Yards ExplainedFind out how many cubic yards or bags of mulch your beds need, the right depth for each situation, and how to avoid mulching mistakes that harm plants.
How Much Topsoil Do I Need? Raised Beds, New Lawns and LevelingCalculate topsoil for raised beds, new lawns and low spots, plan for settling, and choose between topsoil, garden mix and fill dirt.
How to Measure Curved and Irregular Areas for Soil, Mulch or GravelKidney-shaped beds, winding paths and sloped holes are hard to measure. Four practical methods give a volume estimate you can confidently order from.
How Much Does a Cubic Yard Weigh? Soil, Mulch, Sand, Gravel and MoreTypical weights per cubic yard for common landscape and building materials, why moisture matters, and how to check whether your truck or trailer can carry a load.