Advertising Budget
Begin with the monthly amount the business plans to invest.
Loading
Free Tool · MVP Complete · Deployment Pending
LeadMath
A free paid-advertising forecast calculator that models the complete path from ad spend to leads, appointments, customers, revenue, contribution, customer acquisition cost and return on advertising spend.
View Software Products
Launching Soon
The Product
The Problem
Most advertising calculators stop before the business economics begin.
Cost-per-lead and ROAS alone do not explain whether a campaign can become sustainable. Booking rates, appointment attendance, close rates, average sale value and gross margin all change what a business can afford to spend.
LeadMath connects those assumptions into one transparent forecast so agencies, marketers and businesses can examine the full commercial journey before increasing their advertising budget.
Forecast Model
From Budget to Contribution
One calculation follows the full customer-acquisition journey.
The model deliberately includes the operational conversion points between a lead and a paying customer. That makes weak assumptions visible and shows where campaign economics improve or break down.
Leads
Convert budget and expected CPL into projected lead volume.
Appointments
Apply booking and attendance rates instead of assuming every lead converts.
Customers
Use the attended-appointment close rate to estimate acquired customers.
Revenue & Gross Profit
Connect customer volume to average sale value and gross margin.
Contribution & Efficiency
Calculate contribution after ads, CAC, ROAS and break-even limits.
Scenario Planning
Plan for weaker performance.
Tests the campaign against cautious conversion assumptions so the downside is visible before spend grows.
Model the working forecast.
Uses the user’s entered assumptions as the primary planning view and the central reference point for the saved report.
Understand the upside.
Shows how stronger booking, attendance and closing performance can change revenue, contribution and acquisition efficiency.
What LeadMath Calculates
01 · CUSTOMER JOURNEY
Lead-to-Customer Forecast
Projects each stage from lead generation through booked appointments, attended appointments and acquired customers.
- Projected leads
- Booked and attended appointments
- Expected customers acquired
02 · COMMERCIAL OUTCOME
Revenue & Contribution
Applies average sale value and gross margin to distinguish top-line revenue from the value remaining after advertising costs.
- Projected revenue
- Gross profit before advertising
- Contribution after advertising
03 · ACQUISITION EFFICIENCY
CAC & ROAS
Calculates customer acquisition cost and return on ad spend while keeping both metrics in the context of actual margin.
- Customer acquisition cost
- Return on advertising spend
- Maximum sustainable CAC
04 · BREAK-EVEN CONTROL
CPL Limits & Safety Margin
Surfaces how much the campaign can afford to pay for a lead and how far the expected CPL sits from that break-even boundary.
- Break-even cost per lead
- CPL safety margin
- Clear profitability boundary
Projected campaign revenue
Customer volume multiplied by average sale value.
Contribution after advertising
Gross profit remaining after campaign spend is deducted.
Customer acquisition cost
Advertising spend required for each projected customer.
Return on advertising spend
Projected campaign revenue compared with the ad budget.
Maximum break-even lead cost
The lead-cost ceiling supported by the forecast economics.
Cost-per-lead headroom
The distance between expected CPL and the break-even limit.
Product Architecture
A Real Rails Product
Forecast logic, saved data and public reporting have clear responsibilities.
LeadMath is not a static form with client-side arithmetic. The application versions its calculation engine, stores immutable snapshots and renders durable public reports without coupling the core product to a particular email or hosting provider.
01
Domain
Versioned Forecast Engine
Centralized calculation logic with explicit model-version tracking.
02
Data
Immutable Forecast Snapshot
Saved inputs, scenarios and outputs remain stable after creation.
03
Public Access
Random Public Tokens
Non-sequential shareable report URLs avoid predictable record discovery.
04
Delivery
Optional Report Delivery
Mailer and background-job foundations remain behind a feature flag.
05
Security
Public-Surface Hardening
Rate limiting, CSP, browser headers and privacy-focused filtering.
Key Product Decisions
Keep the calculator open.
No account, email gate or forced registration stands between the user and the forecast. The product earns trust by being useful first.
Save a durable snapshot.
A shared report preserves its exact assumptions and results rather than recalculating silently against future code changes.
Present estimates responsibly.
LeadMath explains assumptions and scenarios as planning guidance—not a guarantee of future campaign performance.
My Role & Engineering Approach
End-to-End Ownership
I turned paid-media planning experience into a focused software product.
LeadMath connects my software-development work with more than thirteen years across sales, marketing, advertising and growth. I defined the economic model, product scope, interface, Rails architecture, test strategy and production-hardening work.
- 01 Product problem, audience and MVP boundary
- 02 Campaign model and scenario logic
- 03 Rails models, services, controllers and views
- 04 Public reports, privacy and security controls
- 05 Automated testing, documentation and release audit
Technology
A conventional Rails stack built for clarity.
The stack keeps the calculation model and public-report workflow understandable, testable and independent from provider-specific delivery.
Ruby 3.3.5
Rails 7.1.6
PostgreSQL
Hotwire
Stimulus
Import Maps
Puma
Minitest
Rack::Attack
Development Practice
Make the complete useful path reliable before expanding.
The MVP prioritised calculation integrity, saved reports, responsive presentation, public security and production verification before adding accounts, subscriptions or unnecessary platform complexity.
Production Readiness
Automated Tests
100 tests
Assertions
797 assertions
Final Result
0 failures
Production Audit
Boot & assets verified
Current Stage
MVP Complete · Deployment Pending
The product is complete and technically release-ready.
The forecast engine, calculator, saved reports, responsive interface, security work, metadata, error pages and production verification are complete. Public hosting is the remaining release step.
CalculatorComplete
Shareable ReportsComplete
Security HardeningComplete
Public DeploymentPending
Launch Plan
Release the completed MVP as a free public tool.
LeadMath will remain available without an account or email gate. Its planned production home is leadmath.carywood.co once hosting is confirmed.
Launching Soon
Rails Development · Product Thinking · Paid Media
LeadMath connects practical campaign experience with focused product engineering.
Explore the rest of my software and client work, review the tools directory or start a conversation about useful products and growth systems.