Guides
In-depth articles written to answer the questions people ask before, during and after using a calculator.
Cubic Yards
Open the Cubic Yard Calculator
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 Much Gravel Do I Need for a Driveway? Layers, Depth and TonsPlan a gravel driveway layer by layer: which stone goes where, how deep each layer should be, and how to turn the dimensions into an order in tons.
Types of Gravel Explained: Pea Gravel, #57, Crusher Run, River Rock and MoreA plain-English guide to the most common gravel and crushed stone types, their sizes, weights and best uses, so you can order the right stone the first time.
How Deep Should Gravel Be? Recommended Depths for Every ProjectRecommended gravel depths for paths, patios, driveways, sheds, drainage and decorative beds, with the reasons behind each number and a coverage chart.
Tons vs. Cubic Yards of Gravel: How to Convert and Compare PricesHow many tons are in a yard of gravel, how to convert between tons and cubic yards, and how to compare quotes from suppliers that price differently.Square Footage
Open the Square Footage Calculator
How to Measure the Square Footage of a House, Step by StepMeasure a home's square footage the way appraisers do: from the outside, floor by floor, with the right spaces included and excluded. Includes a worked example.
How to Calculate Square Footage of L-Shaped and Irregular RoomsSplit L-shaped, angled and curved rooms into simple shapes, measure them accurately, and add or subtract areas to get square footage you can buy flooring from.
How Much Extra Flooring to Buy: Waste Factors for Tile, Laminate and HardwoodThe right overage for flooring depends on the material, the layout pattern and the room shape. Use these waste factors to buy enough boxes without overspending.
Square Feet to Square Meters (and Yards, Acres): Conversions and ChartsConvert square feet to square meters, square yards, acres and hectares with exact factors, quick charts and tips to avoid the most common area-conversion mistakes.Concrete
Open the Concrete Calculator
How Many Bags of Concrete Do I Need? 40, 60 and 80 lb Bag ChartsFind how many 40, 60 or 80 lb bags of concrete you need for slabs, posts and footings, with yield charts, worked examples and when to switch to ready-mix.
How Thick Should a Concrete Slab Be? Patios, Driveways, Garages and ShedsTypical concrete slab thicknesses for patios, walkways, garage floors, driveways and equipment pads, plus base, reinforcement and control-joint basics.
How to Order Ready-Mix Concrete: Yards, Slump, Strength and DeliveryWhat to tell the batch plant when ordering ready-mix concrete: volume, strength, slump, additives and site access, plus how to avoid running short.
Concrete for Footings and Post Holes: Sizes, Depth and VolumeCalculate concrete for deck footings, fence posts and continuous footings. Covers frost depth, form tubes, hole sizes and how to total many holes at once.
How to Simplify Ratios: Whole Numbers, Decimals, Fractions and Three TermsStep-by-step methods for simplifying any ratio to lowest terms, including ratios with decimals, fractions, mixed units and more than two parts.
How to Divide an Amount in a Given Ratio (with Money, Time and Mixes)Share money, time or materials in any ratio using the parts method. Includes worked examples, three-way splits, rounding money fairly and common mistakes.
Ratio vs. Fraction vs. Percentage: How to Convert Between ThemRatios, fractions and percentages describe relationships in different ways. Learn when each is used and how to convert part-to-part and part-to-whole correctly.
Cooking with Ratios: Bread, Rice, Coffee and Vinaigrette Without a RecipeLearn the classic kitchen ratios for bread, pie crust, rice, coffee and dressings, and how to scale them up or down for any batch size.Proportion
Open the Proportion Calculator
How to Solve Proportions: Cross Multiplication Step by StepLearn why cross multiplication works, how to solve for x in any position, and how to handle decimals, fractions and word problems without mistakes.
Direct vs. Inverse Proportion: How to Tell Them Apart and Solve EachUnderstand direct and inverse proportion with clear examples, the formulas y = kx and y = k/x, graphs, and a quick test to know which one a problem needs.
Unit Rates and Unit Prices: How to Find the Best BuyCompare prices of different package sizes with unit rates. Learn the formula, handle mixed units and bulk deals, and avoid the traps that make big packs look cheaper.
How to Scale a Recipe Up or Down Using ProportionsDouble, halve or resize any recipe with a single scaling factor. Includes conversions for awkward amounts, tips for eggs and spices, and pan size adjustments.
GCF vs. LCM: What's the Difference and When to Use EachThe greatest common factor and least common multiple are easy to confuse. Learn what each one means, how they're related, and which one a word problem needs.
The Euclidean Algorithm: The Fastest Way to Find the GCFHow Euclid's division method finds the greatest common factor of large numbers in a few steps, why it works, and how to extend it to three or more numbers.
Prime Factorization: Factor Trees, Division Ladders and Divisibility RulesBreak any number into prime factors using factor trees or the ladder method, with divisibility shortcuts and examples of using primes to find the GCF and LCM.AP Lang Score
Open the AP Lang Score Calculator
AP Lang Exam Format: Sections, Timing, Weighting and How It's ScoredA clear breakdown of the AP English Language and Composition exam: 45 multiple-choice questions, three essays, timing, section weights and how the 1–5 score is built.
The AP Lang Essay Rubric Explained: Thesis, Evidence and Commentary, SophisticationUnderstand the 6-point AP Lang essay rubric row by row, what separates a 2 from a 4 in evidence and commentary, and realistic ways to raise your essay scores.
How to Write the AP Lang Synthesis Essay: Plan, Structure and Common MistakesA practical approach to the AP Lang synthesis essay: using the reading period, choosing sources, building a line of reasoning and avoiding source summary.APUSH Score
Open the APUSH Score Calculator
How to Write the APUSH DBQ: Rubric Points, Plan and Paragraph StructureA step-by-step approach to the APUSH document-based question: using the reading period, earning each rubric point, sourcing documents and adding outside evidence.
APUSH Long Essay Question (LEQ): How to Plan and Score WellPlan and write the APUSH long essay question: the 6-point rubric, choosing evidence, structuring causation, comparison and continuity-and-change arguments, and the 2027 update.
APUSH Short-Answer Questions: The ACE Method and the 2027 FormatHow to answer APUSH short-answer questions for full credit: reading the source, the ACE method, specific evidence, timing, and what changes for the 2027 exam.Final Grade
Open the Final Grade Calculator
How Weighted Grades Work: Calculate Your Class Grade Step by StepUnderstand weighted grading categories, calculate your current grade from a syllabus, and see why a high homework average may not lift your grade as much as you think.
Can I Still Pass the Class? How to Find Out and What to Do NextWork out the minimum score you need on the final to pass, understand what happens if the number is over 100%, and plan practical next steps with your instructor.
A Two-Week Final Exam Study Plan Based on the Score You Actually NeedStart with the score you need, then build a realistic two-week plan using retrieval practice, spaced review and past exams. Includes a sample schedule.Molecular Weight
Open the Molecular Weight Calculator
Molar Mass vs. Molecular Weight vs. Formula Mass: What's the Difference?Clear definitions of molar mass, molecular weight, formula mass and atomic mass units, why their numbers match, and how to calculate each from a chemical formula.
Grams to Moles and Moles to Grams: Conversions with Worked ExamplesConvert between grams, moles and number of particles using molar mass and Avogadro's number, with step-by-step examples and a stoichiometry walkthrough.
Percent Composition by Mass: How to Calculate It and Why It MattersCalculate the mass percent of each element in a compound from its formula, check the result, and use percent composition in labs, nutrition labels and fertilizers.PFT Score
Open the USMC PFT Calculator
Marine Corps PFT Scoring in 2026: Tables, Classes and What ChangedHow the Marine Corps PFT is scored in 2026: event minimums and maximums, class thresholds, the sex-neutral standard for combat arms and how to calculate your total.
Pull-Ups or Push-Ups on the PFT? Do the Math Before You ChoosePush-ups cap at 70 points on the Marine Corps PFT, pull-ups at 100. Compare points for your numbers and age group and decide which event is worth training.
How to Increase Your Pull-Ups for the Marine Corps PFTA practical plan to add pull-ups for the PFT: dead-hang standards, grease-the-groove volume, negatives, rows and grip work, with a sample weekly schedule.Chronological Age
Open the Chronological Age Calculator
Why Exact Chronological Age Matters in Standardized TestingHow norm-referenced tests use chronological age to choose the right norm table, why a small error can change a standard score, and how to calculate and record age correctly.
How to Calculate Chronological Age by Hand (and the Mistakes to Avoid)Step-by-step instructions for calculating chronological age on a test protocol using the borrowing method, with worked examples, rounding rules and common errors.
Corrected Age for Premature Babies: How to Calculate It and When to StopWhat corrected (adjusted) age means for babies born early, how to calculate it from gestational age, how long to use it, and how it affects milestones and testing.CD Interest
Open the CD Calculator
How CD Interest Works: APY, Compounding and What You'll Actually EarnUnderstand how certificates of deposit earn interest, the difference between APY and interest rate, how compounding frequency matters, and how to calculate your return.
CD vs. High-Yield Savings Account: Which Is Better for Your Money?Compare certificates of deposit and high-yield savings accounts on rate, access, risk and flexibility, with a worked example and a simple way to decide.
How to Build a CD Ladder: Steady Access, Better Rates, Less Timing RiskBuild a CD ladder step by step, compare it with a single long CD, and see how ladders balance access to cash with higher long-term rates. Includes a worked example.
401(k) Contribution Limits for 2026: Employee, Catch-Up and Total LimitsThe 2026 IRS limits for 401(k), 403(b), 457 and TSP plans: $24,500 employee deferral, $8,000 catch-up, $11,250 for ages 60–63, and the $72,000 total limit.
How a 401(k) Employer Match Works: Formulas, Vesting and Getting the Full MatchUnderstand common 401(k) matching formulas, calculate how much your employer contributes, learn how vesting works, and make sure you don't leave free money on the table.
Traditional vs. Roth 401(k): How to Choose (or Use Both)Compare traditional and Roth 401(k) contributions: when you pay tax, how withdrawals work, required minimum distributions, and how to decide based on your tax rate.