Definitions before inputs
Knowledge guides define symbols, units and assumptions before presenting a formula, helping you identify the values a calculator expects.
CalcOcean reference library
Understand the calculation.
Definitions, variables, assumptions and worked examples. Use these references to understand a formula; visit the blog for practical scenarios and comparisons.
Search the library and toolsFormula versus interactive tool
A guide explains why a relationship works; a calculator applies that relationship to your inputs. Neither replaces rules or advice specific to your situation.
Verify with an example
Follow a worked example, substitute the values into the formula and compare the result with the linked calculator before using unfamiliar units.
Start with the fundamentals
Featured reference
Percentages: the base, the part and the rate
Choose the correct denominator, distinguish percentage points from percentage change, and work backwards from a discounted price.
Featured reference
Compound interest: periods, deposits and assumptions
Understand monthly compounding, end-of-month contributions and the distinction between deposits and interest in a fixed-rate projection.
All guides
Math
Percentages: the base, the part and the rate
Choose the correct denominator, distinguish percentage points from percentage change, and work backwards from a discounted price.
CalcOcean Editorial TeamPublished Updated 5 min read
Fractions: Equivalent Forms and Arithmetic
A reference for numerators, denominators, simplification, common denominators and the four fraction operations with worked examples.
CalcOcean Editorial TeamPublished 5 min read
Ratios and Proportions: Scaling and Sharing
Define part-to-part and part-to-whole ratios, solve proportions, allocate totals and distinguish direct scaling from weighted averages and offsets.
CalcOcean Editorial TeamPublished 5 min read
Percentage Change: Formula, Bases and Comparisons
A reference for relative change, percentage points, repeated changes, reverse changes and cases with zero or negative starting values.
CalcOcean Editorial TeamPublished 5 min read
Finance
Compound interest: periods, deposits and assumptions
Understand monthly compounding, end-of-month contributions and the distinction between deposits and interest in a fixed-rate projection.
CalcOcean Editorial TeamPublished Updated 5 min read
Loan Payment Formula: A Fixed-Rate Reference
Define principal, periodic rate and payment count; derive amortization, calculate a sample payment and identify the model’s exclusions.
CalcOcean Editorial TeamPublished 5 min read
Mortgage Basics: Price, Principal and Monthly Costs
Understand a mortgage calculation from down payment to amortization, and separate principal and interest from wider ownership costs.
CalcOcean Editorial TeamPublished 5 min read
Simple Interest: Principal, Rate and Time
Define the simple-interest formula, convert time units, solve for missing variables and recognize when changing balances require another model.
CalcOcean Editorial TeamPublished 5 min read
Conversions
Temperature Conversion: Celsius, Fahrenheit and Kelvin
Reference formulas for temperature readings and intervals, with variables, inverse checks, absolute zero and practical rounding examples.
CalcOcean Editorial TeamPublished 5 min read
Unit Conversion: Factors and Dimensional Consistency
Convert compatible units through a reference factor and handle squared, cubed and digital units correctly.
CalcOcean Editorial TeamPublished 5 min read
Health
BMI Explained: Formula, Units and Limits
Calculate adult body mass index correctly, understand the limits of a height-and-weight ratio and avoid unit and rounding errors.
CalcOcean Editorial TeamPublished Updated 5 min read
BMR and Resting Energy: Equations and Assumptions
Define basal and resting energy, work through the Mifflin–St Jeor equation, and distinguish resting estimates from activity-adjusted daily needs.
CalcOcean Editorial TeamPublished Updated 5 min read
Business
ROI Formula: Cost, Gain and Time
Define return on investment, reconcile cost and proceeds, calculate losses and distinguish basic ROI from annualized or cash-flow-aware returns.
CalcOcean Editorial TeamPublished 5 min read
Profit Margin: Revenue, Cost and Profit
Distinguish margin on revenue from markup on cost, define the cost boundary and compare like with like.
CalcOcean Editorial TeamPublished 5 min read
Recently expanded guides
- Percentages: the base, the part and the rateUpdated 2026-09-05
- Compound interest: periods, deposits and assumptionsUpdated 2026-09-05
- BMI Explained: Formula, Units and LimitsUpdated 2026-09-06
- BMR and Resting Energy: Equations and AssumptionsUpdated 2026-09-06