Google Ads Budget Calculator for Ecommerce
Ecommerce Google Ads billing runs on purchases, and purchases move the conversion math from leads to transactions: a $60/day budget at a $1.20 CPC is $1,824 a month buying about 1,520 clicks; at a 2.5% purchase rate that is 38 orders at $48 each. The question that decides everything is whether $48 per order clears your margin — and for Target ROAS bidding, whether 38 conversions a month clears Google's recommended data floor.
Model the funnel below, then read the tROAS math: why Google wants 50 conversions a month before its ROAS bidding means anything, and how breakeven CPC sets the ceiling for every bid you make.
Your actual average, from the campaign's 'Avg. CPC' column.
Conversion rate. Leave blank to model traffic only.
Your close rate on leads. Blank = no sales row.
Monthly spend ceiling
$1,824.00
$60.00/day × 30.4 — Google's official monthly cap, however much any single day overdelivers.
- Worst single-day charge
- $120.00
- Clicks per month
- 1,520
- Leads per month
- 38
- Smart Bidding readiness
- Enough data
Google may spend up to 2× your daily budget on one day and compensate on quieter days. A charge above this line is a billing error worth disputing.
50 per day at $1.20 average CPC.
At a 2.5% conversion rate — $48.00 per lead.
Projected conversions clear Google's recommended 30 per month for judging Smart Bidding.
Based on Google's published rules: monthly spend is capped at 30.4× the daily budget, single days may charge up to 2× the daily budget, and Google recommends ~30 conversions per month (50 for Target ROAS) before Smart Bidding results are meaningful. Actual CPCs vary by auction — model with your account's real averages.
Starting values are set for a typical ecommerce scenario — change any field to match yours. Need the plain version? Google Ads Budget Calculator.
From clicks to orders, worked
| Stage | Volume | Unit economics |
|---|---|---|
| Monthly ceiling | $1,824 | $60 × 30.4 |
| Clicks | ≈1,520 | $1.20 each |
| Orders (2.5%) | ≈38 | $48 cost per acquisition |
The tROAS floor, and the margin math beneath it
- Google's guidance: judge Smart Bidding over periods with at least 50 conversions for Target ROAS. 38 orders a month is close but short — consolidating campaigns or counting a longer period closes the gap.
- Breakeven ROAS = 1 ÷ gross margin. At a 60% margin, breakeven ROAS is 1.67; every tROAS target below that buys revenue at a loss. Set targets above it, not at it — the target is a floor, and fees and returns live above it.
- Breakeven CPC = AOV × margin × conversion rate. At $120 AOV, 60% margin and 2.5% conversion: $1.80. A $1.20 actual CPC against a $1.80 ceiling is a healthy 50¢ of headroom; a $1.90 CPC means every click loses money regardless of ROAS impressions.
- Shopping and Performance Max campaigns eat budget in different patterns: PMax spends broadly with less placement control — give it the conversion floor before judging it.
Where ecommerce budgets leak
- Branded shopping terms eat budget defending demand you already own — separate brand and non-brand so each number stays readable.
- Return rates silently inflate ROAS: revenue that comes back as returns still counted at conversion time. Net revenue, not conversion-time revenue, is the honest denominator.
- Seasonal tROAS targets need seasonal revision — the same 400% target that is efficient in February starves delivery in November's auction.
- New products without conversion history drag Smart Bidding through relearning; segment launches from the evergreen campaign until they have sales.
Frequently asked questions
- How much should an ecommerce store spend on Google Ads?
- Enough to clear Google's conversion data floors and your own margin math: Target ROAS wants around 50 conversions per month of data, so at a 2.5% purchase rate that is roughly 2,000 clicks — at a $1.20 CPC, about $2,400 a month. Below that volume, judge campaigns manually or over longer periods.
- What ROAS should I target?
- Above breakeven with room for reality: breakeven ROAS is 1 ÷ gross margin (1.67 at a 60% margin), and the target should sit above it to absorb returns, fees and seasonality. Targets at exact breakeven convert ad spend into revenue at zero profit — the most common misreading of the metric.
- How do I work out breakeven CPC?
- Multiply average order value × gross margin × conversion rate. $120 AOV, 60% margin, 2.5% conversion gives $1.80 — the most any click may cost before it loses money. Compare that ceiling to your actual CPC daily; the gap is your entire safety margin.
- Why did Google recommend 50 conversions for Target ROAS?
- ROAS bidding models revenue values, which are noisier than counted conversions; Google's published guidance is to evaluate it over periods with at least 50 conversions. Below that floor, reported ROAS swings reflect data sparsity rather than bid decisions.
- Should I count returns in my ROAS?
- Yes for anything you act on. Ad platforms report ROAS at conversion time; returned orders inflate it. Pull net revenue from your store for the same period and compute ROAS against that — the gap between platform ROAS and net ROAS is exactly where unprofitable campaigns hide.
- Is Performance Max worth the budget versus Standard Shopping?
- It depends on conversion volume and your appetite for less placement control. PMax spends across every Google inventory and needs the conversion data floor to do its thing; Standard Shopping gives granular bidding per product group. A common split: PMax for the proven best-sellers, Standard Shopping for tests and new lines.