How Subscription Apps Can Use Value-Based Bidding in Google Ads

Ashley Black is a mobile growth consultant at Candid Consulting, specializing in user acquisition and monetization for subscription apps. Here, she breaks down how to implement value-based bidding strategies in Google Ads to optimize for long-term revenue rather than immediate conversions.

What is Value-Based Bidding?

Value-based bidding, also called ROAS (Return on Ad Spend) bidding, is a Google Ads feature that lets you set a target ROAS and have Google's algorithm automatically adjust your bids to maximize revenue rather than conversions.

Instead of optimizing for "cost per install" or "cost per subscription," you're optimizing for "revenue generated per dollar spent." This aligns your ad strategy with your actual business goal: sustainable, profitable growth.

When ROAS Bidding Isn't the Right Choice

Value-based bidding sounds great, but it's not always the right approach. Consider sticking with conversion-based bidding if:

You get fewer than 15 conversions per day: ROAS bidding needs sufficient data to learn. Small volume means high variance and poor optimization.
Your trial period is longer than 7 days: ROAS bidding optimizes based on immediate purchase data. If users take 14+ days to decide, the algorithm doesn't have enough signal to optimize effectively.
You're risk-averse: ROAS bidding can be volatile, especially in the early months. If you need predictable costs, conversion bidding is safer.

For apps that meet these criteria, conversion-based bidding or cost-per-install bidding provides more stability.

Setting Up ROAS Campaigns in Google (3 Steps)

Step 1: Track the Right Events

ROAS bidding requires conversion events with purchase values. In Firebase, set up:

in_app_purchase event: Fire this when a user completes a subscription purchase, with the purchase_value parameter set to the subscription price.
subscription_initialize event: Optional but useful—fire when a user starts a free trial, to help Google understand purchase intent.

Make sure these events are connected to Google Ads via Firebase.

Step 2: Create a Campaign with Target ROAS Bidding

In Google Ads:

Create a new campaign or edit an existing one
Set the bidding strategy to "Maximize conversion value"
Enter your target ROAS (e.g., 3:1 means you want $3 in revenue for every $1 spent)

Start with a conservative target ROAS based on your historical data. If you know you typically achieve 4:1 ROAS, start there. You can adjust as the campaign learns.

Step 3: Let It Learn

ROAS campaigns need a learning period—typically 2-4 weeks. During this time, costs may be higher as Google's algorithm tests different audiences and placements to optimize for your target ROAS.

Don't panic and kill the campaign early. Give it 2-3 weeks of consistent data before evaluating performance.

Challenges and How to Overcome Them

Challenge 1: Scale

ROAS bidding requires scale. If you're getting 5-10 conversions per day, you won't have enough data for good optimization. You need at least 15-20+ conversions daily for stable performance.

Solution: If you're below this threshold, either focus on driving more traffic first, or use conversion bidding until you scale.

Challenge 2: Long Decision Cycles

For apps with 14+ day free trials, users may take weeks to convert. ROAS bidding can't effectively optimize if the conversion happens days after the click.

Solution: Track intermediate events like trial_initialize or free_trial_day_7_reached. These give Google signal sooner. Or use conversion bidding for trial acquisition, then ROAS bidding for paid subscriptions.

Challenge 3: A/B Testing

A/B testing with ROAS campaigns is tricky because the algorithm automatically adjusts bids. A test may be invalid because Google lowered bids in one variant due to perceived underperformance.

Solution: Test at the creative level (different ads, landing pages) rather than bidding strategy. Keep ROAS bidding consistent across test and control groups.

Reporting and Optimization

Key metrics to track:

Actual ROAS: Total revenue ÷ total ad spend. Compare to your target.
Cost per subscription: Total spend ÷ subscriptions. This helps you understand the absolute cost.
Conversion value per click: Total revenue ÷ total clicks. Indicates how valuable your traffic is.
ROAS by network/placement: Are some placements (Search, Display, YouTube) more valuable than others?

If you're consistently under your target ROAS, either lower your target or improve the underlying conversion funnel (paywall, pricing, onboarding). Don't just blame the bidding strategy.

iOS vs. Android: tROAS and SKAdNetwork

On iOS, Apple's SKAdNetwork limits attribution data. Google's tROAS (target ROAS) for iOS is based on limited signals and conversion windows.

Expect ROAS bidding to perform differently on iOS than Android. Test conservative targets on iOS and be prepared for more variance in performance.

Conclusion

Value-based bidding represents a shift from optimizing for volume (cost per install) to optimizing for value (revenue per user). For subscription apps with sufficient scale and fast conversion cycles, ROAS bidding can unlock more sustainable, profitable growth.

Start by ensuring you have the right events set up, scale to 15+ daily conversions, and test a target ROAS based on your historical data. Give it time to learn, and monitor actual ROAS against your target. As you optimize, you'll find the sweet spot that maximizes both revenue and efficiency.