How this Facebook ads budget calculator works
Most people pick a budget by gut feel. A better way is to start with the result you want and work backwards. The calculator does four simple steps:
- Leads needed = customers you want ÷ your close rate.
- Monthly budget = leads needed × cost per lead.
- Daily budget = monthly budget ÷ 30.4 (the average days in a month).
- Return on ad spend = sales from those customers ÷ monthly budget.
A roofer wants 5 new jobs a month. Each job is worth £1,500. He closes 1 in 5 enquiries (20%). Leads cost £25. He needs 25 leads, which is £625 a month, about £21 a day, to bring in £7,500 in sales. That is a 12x return.
The number most people get wrong
It is not the budget. It is the close rate. If you only close 1 in 10 leads because calls go to voicemail or you reply the next day, you need twice the leads, and twice the budget, for the same result. That is why I build AI automation and missed-call text back into every Facebook ads setup. Faster replies mean more of the leads you already pay for turn into customers.
What a real small budget can do
One of my clients has run the same campaign on £10 a day since October. He has spent £3,209.70 and booked 742 enquiries at £4.33 each. Put £4.33 into the cost per lead box above and see what it does to the daily budget you need. Read the full £10-a-day case study, or the guide on what Facebook ads cost in 2026.
Want these numbers for real?
I build the ads, the funnel and the follow-up that make these numbers happen. Book a free 30-minute call and I’ll map it out for your business.
Book a free callFrequently asked questions
How much should I spend on Facebook ads per day?
Work backwards from your goal. Take the customers you want per month, divide by your close rate to get the leads you need, multiply by your cost per lead, then divide by 30. For example, 5 customers at a 20% close rate needs 25 leads. At £25 a lead that is £625 a month, or about £21 a day.
What is a good cost per lead on Facebook?
In WordStream’s 2026 US benchmarks the median across industries was $27.39 per lead, $13.74 for real estate and $42.95 for home improvement. A good cost per lead is any number that still leaves you a profit after your close rate. That is what this calculator checks.
What is the minimum budget for Facebook ads?
Meta lets you run ads from about $1 (£1) a day. In practice most local service businesses start somewhere between £10 and £30 a day so the ads get enough data to learn. One of my clients has booked 742 enquiries on £10 a day.
What return on ad spend should I aim for?
For most service businesses, 3x or more is healthy, meaning every £1 spent brings back £3 or more in sales. Below 1x you lose money on ads alone, so fix the offer, the funnel or your follow-up before you raise the budget.
How do I lower my cost per lead?
Three things move it most: a clear offer, an ad that speaks to one type of customer, and a short landing page or lead form. After that, replying to every lead within minutes and using missed-call text back lifts your close rate, which lowers your cost per customer too.
Related guides
- How much do Facebook ads cost for a small business in 2026?
- Facebook lead ads vs a landing page
- How to build a sales funnel for a service business
- How to hire a Facebook ads expert
Pierce Tagle is a Facebook ads expert and AI automation specialist. He builds the ads, funnels and GoHighLevel follow-up systems that turn clicks into booked calls for businesses in the US and UK. More about Pierce