Please do note that these are technical minimum requirements, not the best practices!

This article outlines the minimum and maximum limits set by Facebook on daily & lifetime budgets, and bid amounts. Trying to update bids or budgets to values that don't comply with these limits will result in an error message.

These limits by Facebook are made with good intentions, as it will prevent choosing bids and budgets that would cause underdelivery.

Smartly.io Triggers and Predictive Budget Allocation try to take these validations into account: for example, if an automated action would otherwise set a daily budget to $0.90, it is set to $1.00 instead. In other words, sometimes when required, PBA, Smart Budget Scheduling or Triggers will make edits that might seem unexpected to you.

Minimum budgets

Disclaimer: this information is listed to Smartly.io's best practise and might be inaccurate. Facebook's documentation is outdated, but can be found here: minimum budgets, maximum budgets

Minimum budgets are calculated as minimum ad set daily budgets – but the same logic applies for lifetime budgets and campaign level budgets (CBO). For lifetime budgets, simply multiply the minimum daily budget by the number of days between your ad set / campaign start time & end time. For minimum CBO budgets, sum the minimum ad set budgets of active ad sets.

For Campaign Budget Optimization (CBO) campaigns – campaign level budgets

The same rules as below apply, but you sum the ad set minimum budgets for every non-archived ad set in the campaign.

In addition, the campaign budget must be higher than the sum of Ad Set Minimum Daily Spend Targets inside the campaign.

Base minimum ad set daily budget

• $1.00 (USD) for ad accounts in currencies USD, AUD, CAD, SGD, JPY, NZD, TWD, EUR, CHF, SEK, HKD, GBP, ILS, NOK, KRW and DKK
• $0.50 (USD) for ad accounts in other currencies

For clarity, those currencies apply to the following countries: Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Greece, Hong Kong, Israel, Italy, Japan, Netherlands, New Zealand, Norway, Singapore, South Korea, Spain, Sweden, Switzerland, Taiwan, United Kingdom, and the United States of America.

When using a bid amount and special billing events

For ad sets that have:

• a bid strategy other than Lowest Cost without Bid Cap (= ad set has a bid amount)
• a billing event other than Impressions

... the minimum ad set daily budget is 500% of your bid amount – for example, 5 times your Bid Cap or Cost Cap. See Facebook Help Center for more details.

For lifetime budgets

The same logic outlined above also applies for lifetime budgets. Simply multiply the value by the number of days between ad set start & end times to get the minimum lifetime budget.

When decreasing the lifetime budget of an ad set or campaign, the new value must be at least +10% greater than the current amount spent already. For example: if an ad set has a $1000 lifetime budget and has spent $300 so far, the minimum new lifetime budget is $330.

Curiously, this +10% rule even applies to ad set level daily & lifetime spend caps in CBO campaigns; Facebook reserves this safety limit to be able to guarantee that the spend cap is not exceeded.

When making edits to ad sets

The above validation logic is also applied when you edit any of the settings that factor into the minimum budget limits. If your budget isn't high enough for the new settings, the change won't go through and you will get an error message.

These actions could increase the minimum budget requirement, and therefore result in an error:

• Changing a bid amount
• Changing the billing event to something else than Impressions
• Extending the lifetime by changing start or end times
• Activating more ad sets inside a CBO campaign

Please do note that these are minimum requirements. Best practice is to have ad set budget higher than 25 x bid amount when optimizing towards conversion Pixels & conversion events. This ensures that Facebook's algorithms gets enough data for optimization purposes.

Maximum budgets

Facebook also has maximum limits for budgets. For USD, AUD, NZD, EUR and GBP this limit is 1 million currency units, but it varies quite a bit between currencies.

The same maximum limit applies to both daily and lifetime budgets – and both ad set and campaign level budgets (CBO).

You can find the full list here: Facebook Marketing API documentation: Ad set budget

Limits for bid amounts

The limits outlined above, between bid amounts and budgets, work both ways. In other words, if your billing event is something else than Impressions, your maximum Bid Cap is 50% of daily ad set budget.

The minimum bid amount is 0.01 for currencies that have sub-units like cents; and 1 for the currencies that don't.