When should you move budget between campaigns?

A low average cost per lead tells you what a campaign achieved with its current budget. It doesn’t tell you what another $500 will buy. Before shifting spend, ask what the next dollars are likely to add, and what the campaign losing budget will give up. This guide gives a simple way to compare campaigns, a worked example and a set of checks that stop you moving money for the wrong reason.

Average and marginal results are different questions

The average cost is total spend divided by total results. The marginal cost is the extra spend divided by the extra results it produced. Campaigns usually return less for each additional dollar as they reach less-interested audiences or higher-priced auctions, so the marginal cost is normally above the average. How much above varies by campaign, which is why moving money based on averages can disappoint.

Work from comparable outcomes

Use the same qualification rule and a mature reporting period. Separate brand from non-brand when their roles differ. Check whether either campaign is limited by demand, geography or the landing page before changing the budget.

• Compare qualified leads or sales, not clicks.
• Use periods long enough for leads to be reviewed.
• Keep brand campaigns apart, since they often capture demand created elsewhere.
• Note any seasonality, promotions or tracking changes in the period.

Check why the campaign is capped

Extra budget only helps a campaign that is held back by it. In Google Ads, look for a “limited by budget” status and for impression share lost to budget. If the campaign already reaches most of the available audience, more budget will not buy proportionally more, and the limit lies in demand, targeting or the offer.

Daily budgets are also averages. Google notes that Smart Bidding may spend up to twice the average daily budget on a given day, so judge pacing over a week or a month, not a single day.

Estimate the next dollars

Campaign A spends $1,000 for 10 qualified leads. Campaign B spends $1,000 for 8. A looks better on average. Suppose a recent $300 increase on A added one qualified lead, while the same increase on B added three.

The observed marginal cost was $300 in A and $100 in B. That is a hypothesis for the next test, and a small sample can easily move either estimate. If A had added two leads instead of one, its marginal cost would have been $150. Treat a result like this as a reason to test, not as proof.

Put guardrails around the move

• Know your ceiling. Write down the maximum cost per qualified lead the business can support. A campaign whose marginal cost is below that ceiling can justify more budget, and one above it cannot.
• Move a size you can reverse. Shift enough to measure, but not so much that you cannot undo it. There is no universal percentage that is right for every account.
• Protect demand capture. Moving budget away from a campaign that captures existing demand can reduce the results of other campaigns that rely on it.
• Allow for delay. If sales takes weeks to qualify leads, the effect of the change will not be visible straight away.

Make the change measurable

1. Write down the outcome and the maximum cost per qualified lead you can support.
2. Change one budget allocation and log the date and reason.
3. Do not change bids, targeting or landing pages at the same time.
4. Wait for sales qualification, then compare incremental results and the volume you lost elsewhere.
5. Decide in advance what result would make you keep, reverse or extend the move.

How to read the result

Common mistakes

• Moving budget because of average cost per lead alone.
• Cutting a campaign that assists others without checking its role.
• Judging a change before leads have been reviewed.
• Changing several things at once, so the cause is unclear.
• Reacting to one very good or very bad day.

Build a starting scenario with the paid media budget planner, and check your inputs with the guide to measuring what a qualified lead costs.