Methodology
How we build, source, and validate every calculator on Calcureal.
Our principle
Every Calcureal tool must produce the same result as a qualified professional using the same inputs. We achieve this by building from primary sources — published formulas, peer-reviewed literature, and official government guidance — not from secondary aggregators or user-submitted content.
Where a formula has multiple accepted variants (for example, Harris-Benedict vs. Mifflin-St Jeor for calorie estimation), we use the more recently validated version, note the difference, and cite both sources.
Validation process
Each tool goes through the following steps before publication:
- Formula sourcing — we identify the authoritative primary source for the formula (peer-reviewed paper, government regulation, or recognised professional body).
- Implementation — the formula is implemented as a pure function in TypeScript with defined input types and edge-case handling (zero, negative, and extreme values).
- Test suite — a minimum of five automated test cases are written, each with expected outputs derived directly from the authoritative source. Tests must pass to tolerance (±0.01% for finance, ±0.1% for health, exact for conversions).
- Expert review — outputs are reviewed by a qualified professional in the relevant field before publication.
- Source citation — every published tool displays its formula source and, for UAE tools, a last-verified date.
Finance & investment
Finance formulas are validated against standard references as used by regulated financial institutions and professional bodies. We do not adjust or interpret formulas — we implement them as specified.
Reference for compound interest, present/future value, and annuity formulas.
Cross-reference for standard financial formulas and plain-language explanations.
UK interest rate reference for mortgage and savings tools.
Health & medical
Health tool formulas are sourced from peer-reviewed clinical literature and validated against published clinical guidelines. Our health tools are reviewed by a licensed medical professional before publication. Reference ranges and classifications follow WHO and NICE standards where applicable.
BMI thresholds and classification used in our BMI calculator.
Mifflin MD et al. (1990) — primary source for the calorie/BMR formula used in our calorie calculator.
UK National Institute for Health and Care Excellence — reference for clinical thresholds.
Standard obstetric formula for estimated due date calculation used in our pregnancy calculator.
UAE legal & regulatory
UAE tools are built directly from enacted legislation and official government publications. Each tool displays the specific law, article, and last-verified date. When legislation changes, we update the tool and its test suite before the new law takes effect.
Primary source for all UAE gratuity (EOSB) and end-of-service benefit calculations.
Official UAE VAT rate (5%) and exemption categories.
RTA fee structures for vehicle-related tools.
Reporting an error
If you believe a tool produces an incorrect result, we want to know. Email us at legal@calcureal.com with the tool name, your inputs, and the result you expected with a source reference. Verified formula errors are corrected within 5 business days and the tool is republished with an updated test suite.