How to add margins to different channels or campaigns using Custom Fields in Windsor.ai

When managing media budgets across multiple advertising platforms, the raw spend reported by those platforms often doesn’t reflect the cost that you want to report or bill. 

You may need to add:

• Service or agency fees
• Reseller markups
• Operational cost multipliers
• Campaign-level strategy adjustments
• Rebate-reduced net costs

Instead of maintaining formulas in every dashboard, you can use Windsor.ai’s Custom Fields to apply a margin multiplier to your spend values either per channel or per campaign type. 

This guide explains when and how to use Custom Fields and shows how to push your new margin-adjusted cost field to Looker Studio, Google Sheets, BigQuery, or other destinations.

A margin is a multiplier applied to your media spend to adjust it before reporting. Margins allow you to show real business-relevant cost values in dashboards, not just raw ad spend.

Formula:

adjusted_spend = spend * (1 + margin_percentage)

Where:

• spend = your raw media spend
• margin_percentage = expressed as a decimal (e.g., 25% becomes 0.25 and the margin multiplier is 1.25).

When applying margins, the goal is to scale the raw spend by a percentage so that every reporting destination receives a consistent adjusted value.

Instead of adding a separate “% margin” column and manually calculating costs in Google Sheets, Looker Studio, Excel, or BI tools, we apply the margin once at the data source layer and simplify the calculation. 

Using a multiplier (such as 1.20 for +20%) is clearer and safer than handling % separately.

You set a fixed margin by source or media platform.

Useful when:

• A standard fee applies across all Google Ads, Meta Ads, etc.
• Billing is based on channel categories like Paid Search or Paid Social.

This model does not depend on campaign naming, which makes it easy to maintain even when campaign structures change.

Margins vary by campaign (service model, reseller vs direct, etc.).

Useful when:

• Each campaign has a different agreement or service model.
• Some campaigns are reseller campaigns, others are direct.

You can also combine both: campaign rules first, then fall back to channel defaults.

In Windsor.ai, Custom Fields allow you to transform or enrich your data before sending it to reporting tools. When applying margins, you can use Custom Metric fields to multiply your raw spend by a margin multiplier.

This ensures that every dashboard and export receives the adjusted values, eliminating the need to add formulas manually in your destination.

1. Go to your windsor dashboard -> Data Preview screen.

2. Select the data sources you’re working with.

3. Click on the plus button below the available fields.

4. Enter a name for your new metric or dimension and create a formula.

Write the formula for calculating the new custom field value from your spend value according to your % of margin. You can apply a margin per channel or per campaign level.

Save and apply.

⚠️ Since margin-adjusted spend is a calculated cost value, always choose NUMERIC.

• Use NUMERIC for any value you want to use in calculations, such as spend, CPA, ROAS, CPC, etc.
• Select TEXT only if your custom field is a label. For example, when tagging campaigns as Brand, Performance, or Retargeting, and not something that will be used in calculations. Text fields can’t be summed, added, or used in mathematical formulas.

5. Once created, this new field can be pushed to any data destination, like Google Sheets, Looker Studio, BigQuery, Power BI, Tableau, Excel, etc., like a normal field. 

6. After creating the field, verify the result of the formula in the destination. You will now have a custom field for your adjusted spend. No need to recreate formulas in dashboards.

Note: For all the examples, we will be using margin multipliers. According to your % margin, please calculate your multiplier value as per the formula mentioned in the beginning of this guide. 

Let’s say your agency charges different service fees for each platform.

• Google Ads: 20%
• Facebook Ads: 30%
• Bing Ads: 15%

Formula:

spend * to_float(
  lookup(
    coalesce(datasource, ""),
    '[ ["google_ads", "1.20"], ["facebook", "1.30"], ["bing", "1.15"] ]',
    '1',
    'eq'
  )
)

If spend = $100 on Facebook: 100 × 1.30 = $130

In case you want to apply the margin only to paid media channels.

For example,

• Google Ads & Facebook: 25%
• Other sources: No margin

Formula:

spend * to_float(
  lookup(
    coalesce(datasource, ""),
    '[ ["google_ads", "1.25"], ["facebook", "1.25"] ]',
    '1',
    'eq'
  )
)

If spend = $200 from Google Ads: $200 × 1.25 = $250

If spend = $50 from other channels: $50 × 1 = $50 (no margin applied)

If you don’t want to apply a margin to organic or direct traffic.

The rule:

• Organic or Direct traffic: 0%
• Apply margin to all other channels: 25%

Formula:

spend * to_float(
  lookup(datasource,
    '[["direct","1"],["organic","1"],["email","1"]]',
    '1.25',
    'eq'
  )
)

If spend = $100 for paid channel: $100 × 1.25 = $125

Define the field that correctly represents this traffic and replace the “datasource” field with it.

Let’s say you have a campaign named “Campaign A”; this specific campaign should include a 30% margin. All other campaigns should remain unadjusted.

Formula:

spend * 
if(
  'Campaign A' in campaign_name,
  1.30,
  1
)

This is a direct string match. The margin only applies to this campaign and not to any others.

In case you want to apply different margins depending on the type of campaign.

For example, 

• Lead generation campaigns: 35% 
• Brand campaigns: 15%
• Retargeting campaigns: 10%
• All other campaigns: No margin

You can use a lookup with the “contains” operator to locate those campaigns.

Formula:

spend * to_float(
  lookup(campaign_name,
    '[ ["pmax", "1.35"], ["brand", "1.15"], ["retarget", "1.10"] ]',
    '1',
    'contains'
  )
)

Applying margins directly in Windsor.ai using Custom Fields allows you to adjust your media spend values before they reach your dashboards or other reporting destinations. This means you no longer need to maintain separate spreadsheets, manual markup calculations, or repeated formulas across different BI tools.

As your campaign strategy, pricing, or fee models evolve, you can simply update the formula in Windsor.ai, and the change will propagate automatically to all connected destinations upon refresh. 

This guarantees long-term maintainability and reduces the risk of inconsistencies in reporting