A shared budget is a single daily amount in Google Ads that several campaigns draw from together, instead of each campaign having its own separate daily budget. Google moves the money between those campaigns during the day, sending more to whichever is finding more chances to show ads.
How a shared budget works
You create the budget once, give it a name and an average daily amount, then assign campaigns to it. From that point the campaigns stop having budgets of their own. Say a roofing firm in Bristol runs three search campaigns, for repairs, new roofs and guttering, and puts all three on a £60 shared budget. On a stormy Monday the repairs campaign may take most of the £60; on a quiet Thursday the spend may spread more evenly.
The normal Google Ads budget rules still apply. Spend can run above the average on busy days, up to twice the daily amount, while Google keeps the month’s total within the daily figure multiplied by the average number of days in a month. A shared budget changes who gets the money, not how much the account can spend.
Shared budgets live in the shared library, and you can also create one from the budget field when editing a campaign. Not every campaign type can join one, and some features, such as campaign experiments, need their campaign to have its own budget. Google Ads shows which campaigns are eligible when you assign them.
Why it matters
For a small account the appeal is simple: one number to manage. If you have six low-volume campaigns, each with a budget of a few pounds that it rarely spends, pooling them stops money sitting unused in one campaign while another is limited by budget.
The cost is control. A shared budget hands the decision about where your money goes to Google, and the campaign that can spend the most is not always the one that earns the most. A broad, generic campaign with lots of search volume can soak up the pool before your brand campaign, which converts cheaply, gets its share. For most businesses the question is not “how do I spend my budget?” but “how do I make sure the best campaigns are never short?”, and a shared budget makes that harder to answer.
Common mistakes
- Putting brand and non-brand campaigns on the same shared budget, so cheap brand clicks lose out to expensive generic ones.
- Pooling campaigns with very different goals, such as lead generation and video awareness, then judging them by one cost per lead.
- Forgetting that a campaign on a shared budget has no budget of its own, then being surprised when pausing one campaign hands more money to the others.
- Using a shared budget to hide a structural problem. If every campaign is starved, the account needs fewer campaigns or more money, not a pool.
- Assuming a shared budget sets the bids. Bidding is separate; a portfolio bid strategy is the tool that shares a bidding goal across campaigns.
How to act on it
Group campaigns on a shared budget only when they share a goal, a margin and roughly the same value per conversion, and when none of them is so important that it must be protected. Keep your brand campaign and your most profitable campaigns on their own budgets.
Check the result weekly for the first month. Look at how the spend actually split between campaigns, and compare each campaign’s cost per conversion with what you would have chosen. If the pool is favouring the weaker campaign, take it out. For a broader view of where money should go, read about budget allocation. Deciding how budgets are structured is one of the first things I review when I take over ongoing PPC management of an account.