The online advertising budget is no longer just about setting a monthly amount and monitoring clicks. Since March 2024, the rollout of Consent Mode v2 by Google has changed the amount of usable data for European advertisers. The same investment can now yield very different measured results depending on the technical consent configuration.
Estimating and optimizing an online advertising budget in 2024 requires taking this reality into account even before choosing a platform or campaign objective.
Consent Mode v2 and advertising budget: the parameter that spreadsheets ignore
Since March 2024, Google requires the transmission of additional signals, including ad_user_data and ad_personalization, to maintain measurement, remarketing, and personalization functions for users in the European Economic Area. Without this configuration, certain audiences become unusable, and conversions are no longer attributed to campaigns.
The problem is concrete: an advertiser who has not updated their consent banner may notice a decline in measured conversions without any decrease in actual sales. The budget then appears to be less effective, while it is the measurement that has degraded. Conversely, a properly configured site receives more signals and can optimize its automatic bids with more reliable data.
Before setting a budget, ensure that your consent infrastructure is transmitting these signals correctly. A technical audit of a few hours can prevent weeks of misattributed spending. To delve deeper into the cost mechanics by platform, the Hi Business guide details the rates and pricing logic specific to each channel.
Target cost per acquisition: starting from the result, not the channel
The most reliable method for estimating an advertising budget is to think backwards. Instead of asking how much to invest in Google Ads or Meta Ads, the starting question is: how much can a conversion (sale, lead, registration) cost while remaining profitable?
This target cost per acquisition (CPA) depends on your unit margin. If your net margin per sale is known, the maximum acceptable CPA corresponds to the fraction of that margin you are willing to allocate to acquisition. The rest of the estimate follows: by multiplying the target CPA by the number of targeted conversions, you obtain an overall budget.
Why the CPA reported by platforms is no longer sufficient
Consent refusals and the gradual end of cross-site tracking reduce directly attributable conversions. Platforms now model a portion of conversions instead of measuring them directly. The ROAS displayed in your Google or Meta dashboard is therefore partly based on statistical estimates.
To strengthen your budget estimation, cross-reference platform data with your internal data: actual revenue, gross margin, number of CRM transactions. A significant discrepancy between reported conversions and actual sales indicates that modeling is skewing your budget reading.
- Import your offline conversions (in-store sales, contract signings, qualified calls) into your advertising accounts to enrich optimization signals.
- Use enhanced conversions that transmit hashed data to improve attribution without relying solely on cookies.
- Monthly compare the CPA reported by the platform with the actual acquisition cost calculated from your accounting.
Budget allocation between Google Ads, Meta Ads, and other channels
The appropriate allocation depends on the intent of the target audience. Google Ads captures existing demand: the user is actively searching for a product or service. Meta Ads (Facebook, Instagram) generates demand: the user discovers an offer in their news feed without having searched for it.
For an e-commerce business with a wide catalog, a balanced allocation between the two is often relevant. Google Shopping and Search capture buyers close to making a decision, while Meta feeds the top of the funnel with prospecting and retargeting.
For lead generation activities (B2B services, training, real estate), Meta Ads with its native forms (Lead Ads) often produce a higher volume of contacts at a lower cost. However, the quality of these leads may be lower than that of contacts from Search, where intent is more pronounced.
Channels not to overlook in estimation
LinkedIn Ads remains expensive per click but relevant for highly qualified B2B targets. YouTube, integrated into Google Ads, offers controlled costs per view for awareness objectives. The budget should reflect the value of the customer acquired by channel, not just the lowest cost per click.
Optimizing an online advertising budget without increasing the envelope
Budget optimization does not always involve increasing spending. Several levers can improve the performance of an existing budget.
Properly configured consent directly improves measured performance. A site that moves from a low advertising consent rate to a properly optimized rate (clear banner, explicit choice, no dark patterns) recovers remarketing audiences and conversion signals that were lost.
The structure of campaigns also plays a crucial role. Grouping too many keywords in the same ad group dilutes the budget across low-profit queries. Isolating high-intent terms in dedicated campaigns with specific bids concentrates spending on searches closest to conversion.
- Regularly exclude irrelevant search terms (negative keywords) to avoid unnecessary spending on Google Ads.
- Test different ad creatives on Meta: a visual variation can significantly reduce the cost per result without changing the budget.
- Analyze the times and days of broadcasting to concentrate the budget on slots where the conversion rate is highest.
- Monitor frequency of exposure on Meta: beyond a certain threshold, repetition degrades performance and wastes the budget.
An online advertising budget in 2024 is managed with three benchmarks: a target CPA grounded in accounting reality, a consent infrastructure compliant with Consent Mode v2, and tracking that cross-references platform data with actual business results. The accuracy of measurement determines the relevance of every euro spent.
