About & Quantitative Methodology

The Calculatorium (https://thecalculatorium.com) is an independent open-formula financial, statistical, e-commerce, and SaaS modeling publication developed and maintained by The Calculatorium Quantitative Research & Engineering Desk (Digital Financial Reference & Decision-Support Systems).

01 // Open-Formula Transparency & Pre-Rendered Accuracy

Many online calculator directories hide their underlying equations or rely on generic one-size-fits-all templates. On The Calculatorium, every tool displays its exact algebraic or statistical equation directly below the results, pre-computes baseline outputs and 5-tier sensitivity tables at build time, and provides a step-by-step worked numerical derivation using real numbers.

02 // 44 Specialized Mathematical Engines

Our 205 calculators are powered by 44 domain-specific mathematical kernels:

• Payment & FX Fee Gross-Up (payment_fee, kdvStopajSerbestMeslek): Models combined domestic base rates, cross-border/FX surcharges, fixed per-transaction fees, B2B reverse invoice gross-up ReverseGross = (TargetNet + Fixed) / (1 - BaseRate - IntlRate), and Turkish GVK Art. 94 Serbest Meslek Makbuzu (SMM) gross-to-net withholding and VAT accounting.
• E-Commerce & Marketplace Unit Economics (ecom_profit, trMarketplaceProfit): Models landed COGS, platform referral commissions, fulfillment/shipping fees, VAT net-off, return erosion, unit contribution margin, and minimum Break-Even ROAS without hidden gateway assumptions.
• Stochastic Forecasting, Econometrics & Data Science ROI (monteCarloRevenue, linearRegressionForecast, churnSurvival, paretoConcentration, cohortRetention, exponentialSmoothing, dataHygieneRoi, scrapingProxyCost, mlModelRoi): Implements seeded Mulberry32 + Box-Muller Geometric Brownian Motion (GBM) simulations, Ordinary Least Squares (OLS) with Student-t 95% prediction intervals, discrete survival hazard curves, Pareto power-law Lorenz/Gini concentration, Simple Exponential Smoothing (SES) with MAE/RMSE/MAPE, and confusion-matrix (TP/FP/FN) cost-benefit ROI.
• Real Estate & Commercial Lease Underwriting (airbnbArbitrage, capRateCashOnCash, leaseVsBuy, nnnLease, house_flip_70, loan_amortization): Separates unlevered NOI Cap Rate from levered Cash-on-Cash return and DSCR, models discounted NPV of buying vs leasing with equity build and resale friction, and calculates commercial Triple-Net (NNN) pass-through escalations.
• Quantitative Risk, Sharpe, Kelly & Market Microstructure (kelly_criterion, sharpe_ratio, positionSizer, evDecisionTree, makerTakerFee, dexSlippageMev, futures_liquidation, impermanent_loss): Implements J. L. Kelly Jr.'s (1956) allocation equation, William F. Sharpe's (1966) ratio, fixed-fractional stop-loss position sizing, constant-product AMM price impact + MEV sandwich exposure, and order-book Maker/Taker round-trip breakeven.

03 // Primary Data Sources & Benchmark Citations

Industry quartile benchmarks and default rate parameters are compiled from publicly verifiable primary sources, including:

• Official merchant fee schedules published by Stripe, PayPal, Adyen, Square, Apple App Store, Amazon FBA, iyzico, and Trendyol.
• Official API token pricing documentation from Anthropic (Claude Sonnet & Opus), OpenAI (GPT series), and Google DeepMind (Gemini).
• KeyBanc Capital Markets Private SaaS Survey, Bessemer Venture Partners Cloud Index, U.S. IRS Publication 550, and T.C. Gelir İdaresi Başkanlığı (GİB) tax schedules.
• Peer-reviewed statistical and quantitative literature (Fisher 1925, Neyman & Pearson 1933, Kelly 1956, Sharpe 1966, Hyndman & Athanasopoulos FPP3, Uniswap v2/v3 Core Whitepapers).

04 // Editorial Contact & Corrections Policy

If you identify a rate schedule update or wish to request a new domain formula, contact our editorial engineering team at editorial@thecalculatorium.com.