The Intermediate level introduced the idea: the strategy's target and the business target are two different things, and they can be in different modes — a campaign bidding on CPA while the business measures it on ROAS. This lesson develops that "cross-mode": when it happens, how you translate between modes and when it is better to change the strategy.
The four cases
1. Leads of uneven value, strategy on CPA
Acquisition where some leads are worth ten times more than others, but the campaign is on target CPA (because there were no values when it was built). The business judge needs ROAS (value of the qualified leads or sales / cost). Hitting the CPA can mean losing money if the cheap leads are the bad ones.
2. Ecommerce judged on new customers
Campaign on target ROAS (order value), but the business wants cost per new customer (repeat business inflates the order value of existing customers). The judge needs the CPA of new customers.
3. Brand on impression share, judged on CPA
Brand campaign on target impression share (it does not optimise to conversions), but the business wants to know that its CPA is still low. The judge works in CPA even though the strategy has no CPA target.
4. Maximising without a target
Campaign on maximise conversions or value (no target): there is nothing to "hit" in the strategy, but there is a business target (CPA or ROAS) to judge.
In all four, the judge (lesson 3) uses its mode and its reference conversions, and translates the verdict into a move of the strategy's target in the strategy's mode.
Translating between modes
To move a CPA target when the goal is ROAS (case 1):
Actual ROAS = reference value / cost
If actual ROAS < target ROAS → the cost per conversion has to come down:
new tCPA = current tCPA × (actual ROAS / target ROAS) (capped at −10/−15%)
If actual ROAS > target ROAS → room for volume:
new tCPA = current tCPA × (actual ROAS / target ROAS) (capped at +10/+15%)
To move a ROAS target when the goal is CPA (case 2): the symmetrical version with
target CPA / actual CPA. Always with capped steps (10-15%), a large enough
window and a wait between moves: the translation is approximate because
the relationship between CPA and ROAS depends on the average value, which changes.
When to change the strategy instead of judging across modes
Cross-mode is a bridge, not a destination. Change the strategy to the business's mode when:
- There are reliable values and volume (50+ conversions with value a month) → move from target CPA to target ROAS (case 1).
- There is new customer data (lists) → switch on new customer value bidding (case 2).
- The brand campaign genuinely competes and impression share is no longer the goal → target CPA/ROAS (case 3).
- Maximising without a target now has volume → add a target (case 4).
And keep the cross-mode when changing strategy would reset a learning phase you cannot afford right now (peak season), or when the values are not trustworthy yet.
Reference conversions by mode
| Judge's mode | Reference conversions | Metric |
|---|---|---|
| CPA | The ones that mean contact/customer (qualified, sale) | cost ÷ number |
| ROAS | The same ones, with a value (real value, offline if needed) | value ÷ cost |
| New customers | Only those from users not present in your lists | cost ÷ new customers |
If the reference conversions have no value, no ROAS judge is possible: Measurement II first.
Cross-mode mistakes
- Judging on ROAS with the tag's value (forms with a fixed value): that is CPA in disguise.
- Translating targets in big steps: the CPA↔ROAS relationship is not linear.
- Changing the judge's mode every month.
- Forgetting that the strategy is still optimising in its mode: if the campaign is on CPA, Google chases conversions; a ROAS judge only corrects the target, it does not change what Google is chasing.
💡 Ninja trick: the Smart Bidding judge (SBNS) stores per campaign the mode of the business target (CPA or ROAS) independently of the strategy, with its reference conversions (both lists: the ones counted by number and the ones counted by value), works out compliance in the business's mode and translates the move into the strategy's mode with capped steps. Cross-mode out of the box, no translation spreadsheet required.
What you should remember
- Cross-mode = strategy in one mode, business in another; four common cases.
- Translate with
actual ROAS / target ROAS(or the inverse), steps of 10-15%, a window and a wait. - It is a bridge: change the strategy to the business's mode when you have values, volume and the right moment.
- Without reliable values there is no ROAS judge: measurement first.