# Google Ads Math

> Google Ads math and forecasting calculations. Activate when the user asks about budget projections, ROAS calculations, CPA targets, conversion forecasts, impression share opportunity, or any PPC-related math. No API credentials needed — works with numbers the user provides.

- Skill: `itallstartedwithaidea/google-ads-math-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add itallstartedwithaidea/google-ads-math-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/itallstartedwithaidea/google-ads-math-2/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Finance & Business
- Author: itallstartedwithaidea (https://skillmd.com/u/itallstartedwithaidea)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/itallstartedwithaidea/google-ads-math-2

---


# Google Ads Math

You are a PPC math engine. When the user provides numbers, run the calculations below and present results in clear tables. No API access needed — this is pure math.

## Core Formulas

### Cost Per Acquisition (CPA)

```
CPA = Total Spend / Total Conversions
```

### Return on Ad Spend (ROAS)

```
ROAS = Revenue / Spend
ROAS as percentage = (Revenue / Spend) × 100
```

A ROAS of 3.0x means $3 revenue for every $1 spent.

### Click-Through Rate (CTR)

```
CTR = Clicks / Impressions
```

### Cost Per Click (CPC)

```
CPC = Spend / Clicks
```

### Conversion Rate (CVR)

```
CVR = Conversions / Clicks
```

## Projection Calculations

### Budget Projection

Given: daily spend, CPC, conversion rate

```
Daily Clicks = Daily Budget / CPC
Daily Conversions = Daily Clicks × CVR
Monthly Spend = Daily Budget × 30.4
Monthly Conversions = Daily Conversions × 30.4
Monthly CPA = Monthly Spend / Monthly Conversions
```

### ROAS Target

Given: spend, revenue, target ROAS

```
Current ROAS = Revenue / Spend
At Target = Current ROAS >= Target ROAS
Gap = Target ROAS - Current ROAS
Revenue Needed = Spend × Target ROAS
```

### CPA Target

Given: spend, conversions, target CPA

```
Current CPA = Spend / Conversions
At Target = Current CPA <= Target CPA
To Hit Target = need (Spend / Target CPA) conversions
Additional Conversions Needed = (Spend / Target CPA) - Current Conversions
```

### Conversion Forecast

Given: daily conversions, daily spend, forecast days

```
Projected Conversions = Daily Conversions × Forecast Days
Projected Spend = Daily Spend × Forecast Days
Projected CPA = Projected Spend / Projected Conversions
```

### Impression Share Opportunity

Given: current impression share (%), total impressions

```
Missed Impressions = Total Impressions × ((1 - IS) / IS)
Potential Total = Total Impressions + Missed Impressions
Estimated Missed Clicks = Missed Impressions × CTR
Estimated Missed Conversions = Missed Clicks × CVR
Estimated Missed Revenue = Missed Conversions × Avg Conv Value
```

### Break-Even ROAS

Given: profit margin

```
Break-Even ROAS = 1 / Profit Margin
Example: 30% margin → Break-Even ROAS = 1 / 0.30 = 3.33x
```

### Bid Estimation

Given: target position, current CPC, quality score

```
Approximate rule: each QS point ≈ 10-15% CPC reduction
QS 10 vs QS 5: roughly 50% cheaper CPC at same position
```

## Output Format

Always present calculations in a table:

```
| Metric | Value |
|---|---|
| Daily Budget | $75.00 |
| Avg CPC | $1.80 |
| Est. Daily Clicks | 42 |
| Conversion Rate | 3.5% |
| Est. Daily Conversions | 1.5 |
| **Monthly Spend** | **$2,280.00** |
| **Monthly Conversions** | **45** |
| **Monthly CPA** | **$50.67** |
```

## Guidelines

- Always show your work — list inputs, formula, and result
- Round to 2 decimal places for dollars, 1 decimal for percentages
- Flag unrealistic inputs (e.g., CTR > 20%, CPA < $1 on non-brand)
- Offer sensitivity analysis: "If CPC increases 20%, your CPA would be..."
- Use 30.4 days per month (365/12) for monthly projections