Empirical B2B Engineering & Financial Calculators

Pure client-side calculation engines designed by Aftab M. for systems architects, finance leads, and founders. Zero tracking, zero signup walls, and 100% mathematical transparency.

TAX & LEGAL COMPLIANCE

⚖️ 2026 SaaS Economic Nexus Risk Calculator

Audit state-by-state gross sales ($100k/$500k) and discrete invoice counts against post-Wayfair statutory traps across 45 states.

Read Full 1,400-Word Nexus Teardown →

Target State Jurisdiction Select any of the 45 US states with post-Wayfair sales tax rules.

Monthly SaaS Revenue in State ($) Gross monthly subscription billings in this state.

Average Plan Price / Subscription AOV ($) Average invoice size (e.g. $49/mo self-serve plan).

Monthly Discrete Invoices / Transactions (#) Discrete annual transactions (triggers 200-count rule).

⚠️ NEXUS TRIPPED: MANDATORY REGISTRATION REQUIRED

You crossed the 200-transaction count threshold in Illinois (2,076 tx/yr vs 200 threshold). You are legally obligated to register with the Illinois Department of Revenue.

Annualized Revenue vs. Threshold: $102,000 / $100,000
Annualized Transactions vs. Trap: 2,076 / 200 tx
State SaaS Taxability: TAXABLE IN IL
Est. Annual Tax Remittance Obligation: $8,925/yr

State Law Note: Chicago imposes a 9% Personal Property Lease Transaction Tax on SaaS in addition to state collection requirements.

FINTECH UNIT ECONOMICS

💳 Stripe Direct vs. Merchant of Record Simulator

Calculate the exact MRR revenue inflection point where direct Stripe (2.9% + 30¢ + CPA retainers) beats Lemon Squeezy / Paddle (5% + 50¢).

Read Full 1,400-Word Tax Math Teardown →

Monthly Recurring Revenue (MRR) ($) Gross monthly subscription billings.

Average Plan Price / Subscription AOV ($) Average invoice price (determines fixed transaction spread).

International & Cross-Border Sales Volume (%) Volume subject to EU/UK VAT and Stripe 1.5% cross-border fees.

Annual Multi-State & Global Tax CPA Retainer ($) Accountant filing costs + Anrok/TaxJar software subscriptions.

MERCHANT OF RECORD IS MATHEMATICALLY CHEAPER

At $45,000 MRR, paying 5% to an MoR is cheaper than hiring tax CPAs and registering in 40+ global jurisdictions yourself. Stick with Paddle / Lemon Squeezy until reaching ~$115,000 MRR.

Stripe Direct Total (Processing + Tax + CPA): $3,150/mo ($37,800/yr)
Merchant of Record Total (5% Flat): $2,503/mo ($30,036/yr)
Net Monthly Profit Difference: SAVE $647/mo WITH MoR
Break-Even Crossover Revenue: ~$115,000 MRR

Unit Economics Rule: Direct Stripe becomes profitable only when subscription volume spreads outweigh the fixed $15,000–$25,000/yr cost of tax accountants and automated compliance filings.

CLOUD OBSERVABILITY TCO

📊 Datadog vs. Self-Hosted OpenTelemetry / Grafana TCO Calculator

Compare the $30k/mo Datadog custom metrics tax against running an in-house Prometheus, Mimir & Loki cluster on AWS.

SRE COST OPTIMIZATION

Monitored Kubernetes / EC2 Host Count (#) Nodes running Datadog Agent with APM Pro ($31/host/mo).

Custom Metric Series Ingested (#) Billable custom metrics ($5.00 per 100 metrics above baseline).

Daily Log Volume Ingested (GB/day) Log volume subject to ingestion + 15-day indexing fees.

OPENTELEMETRY + GRAFANA SAVES $61,500/YEAR

At 35 hosts and 80 GB/day log volume, Datadog custom metric and log indexing markups cost $6,285/mo. Moving to self-hosted Grafana Mimir & Loki saves ~$61,500 annually.

Datadog Monthly SaaS Bill: $6,285/mo ($75,420/yr)
Self-Hosted AWS Grafana Stack (Infra + S3): $825/mo ($9,900/yr)
Estimated Annual TCO Savings: $5,460/mo ($65,520/yr)

Observability Rule: Datadog pricing scales super-linearly with cardinality and log volume. OpenTelemetry provides 100% vendor-neutral metric collection without lock-in.