How to work out how much you should spend on Google Ads each month

TL;DR Most businesses set their Google Ads budget backwards. They start with how much they think they can afford instead of what a customer is actually worth. This post shows how to reverse engineer the right Google Ads spend using customer lifetime value, cost per acquisition and realistic conversion rates.

Why most Google Ads budgets fail

Many business owners pick a monthly Google Ads budget based on gut feel or last month’s leftover cash. That approach rarely delivers strong marketing ROI. The smarter path is to start with your real commercial numbers. When your Google Ads strategy is built on customer value instead of guesswork, every dollar works harder and scaling becomes far more predictable.

Start with your economics, not your budget

Your Google Ads spend should be a direct outcome of three clear numbers:

• Customer lifetime value (LTV)
• Acceptable cost per acquisition (CPA)
• Number of customers you can profitably serve each month

Get these right first and the budget almost sets itself.

Know your customer lifetime value (LTV)

LTV is the total revenue a typical customer generates over the time they stay with you. A single $500 purchase is very different from a customer who pays $200 per month for 12 months ($2,400 total). The higher and more reliable your LTV, the more you can afford to invest to win that customer. This single figure changes how you think about Google Ads budget and business growth strategy.

Define your acceptable CPA

Once you know LTV, decide how much of that value you are willing to spend to acquire the customer. Many businesses target a CPA of 10 to 20 percent of LTV after considering margin and other costs. For example, if a customer is worth $3,000 over their lifetime, you may be comfortable paying $300 to $500 to acquire them. That figure becomes your target cost per acquisition.

Translate CPA into a monthly Google Ads budget

The maths is straightforward. Target CPA multiplied by the number of customers you want equals your monthly budget. Example:
Target CPA = $300
Desired customers per month = 10
Google Ads budget = $3,000 per month

This approach ties your Google Ads spend directly to commercial outcomes rather than arbitrary limits.

Fix your conversion foundation before you spend

Even the best ads will produce poor results if your landing pages do not convert. Before you commit serious Google Ads budget, strengthen these basics:

• Clear offer and positioning that matches search intent
• Strong trust signals such as reviews and testimonials
• Simple, benefit-focused headlines
• Frictionless forms or checkout processes
• Relevant lead magnets where appropriate

Poor conversion rates drive up your cost per acquisition no matter how well the ads perform. Conversion rate optimisation therefore improves profitability across both paid and organic marketing.

Start with controlled testing

Do not jump straight into a large monthly spend. Begin with $500 to $1,000 per month and run the campaign for one to three months. The goal at this stage is clean data, not rapid scaling. Focus spending on high intent keywords using exact match. Target bottom of funnel searches that show clear purchase or booking intent.

For an alternative medicine clinic this might include terms such as:

• "alternative medicine clinic near me"
• "natural medicine doctor sydney"
• "integrative medicine consultation"
• "holistic doctor appointment"

Keep the campaign tight. Spreading a small budget too thinly usually produces unreliable data.

Scale based on proven performance

Once you have confirmed your target CPA (or better) and are happy with lead quality, increase the budget in controlled steps. Scale based on actual results, not assumptions. Continue to monitor conversion rates and customer quality as you grow the Google Ads spend.

The power of conversion rate optimisation

Improving your conversion rate directly lowers CPA and lifts marketing ROI. Small gains in conversion often have a bigger impact on profitability than ad tweaks alone. The best part is that these improvements benefit every traffic source, not just Google Ads.

Model your numbers before you scale

The most practical step you can take is to model your own LTV and CPA scenarios before committing larger budgets. We created a simple calculator to help business owners do exactly that. It lets you test different inputs and see what monthly Google Ads spend actually makes commercial sense for your business. Try the calculator here: Google Ads LTV Calculator

Final thoughts

Setting the right Google Ads budget does not need to be guesswork. When you base your spend on real customer value, acceptable CPA and solid conversion rates, you move from hoping for results to expecting them. This approach supports sustainable business growth strategy and protects your marketing ROI as you scale.

If you would like help reviewing your current Google Ads performance or building a clear, numbers-backed growth plan, feel free to get in touch. We are happy to have a straightforward conversation about what is working and what can improve.