Alex Czartoryski

Conversion rates can vary a great deal across devices, and so it makes sense to bid differently for Mobile vs Desktop vs Tablet. Here two methods to calculate your bid adjustment, as well as an automated bidding script that will do all the work for you!

Calculating based on Conversion Rates

The simplest way is to calculate bid adjustments based on the individual device conversion rates relative to the Campaign average

Calculating based
on Click Value

I believe a more correct way is to calculate bid adjustments based on the relative per click values of each device (the Conv. Value / Click column)

Example Using Real Data

Sample Campaign

Automating Bid Adjustments

Below is a Google Ads Script that will automatically make these adjustments for you (based on relative conversion rate). You can download the latest version of this script on GitHub here:
Google Ads Device Bid Adjustment Script

// Version: 1.13.1 Muppet
// Latest Source: https://github.com/Czarto/Adwords-Scripts/blob/master/device-bid-adjustments.js
//
// This Google Ads Script will incrementally change device bid adjustments
// based on conversion rates using the Campaign's average conversion rate
// as a baseline.
//

/***********

MIT License

Copyright (c) 2016-2021 Alex Czartoryski

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

**********/

var LABEL_PROCESSING_DESKTOP = "_processing_desktop";
var LABEL_PROCESSING_MOBILE = "_processing_mobile";
var LABEL_PROCESSING_TABLET = "_processing_tablet";

var BID_INCREMENT = 0.05;       // Value by which to adjust bids
var MIN_CONVERSIONS = 10;       // Minimum conversions needed to adjust bids.
var MAX_BID_ADJUSTMENT = 1.90;  // Do not increase adjustments above this value



function main() {
    initLabels(); // Create Labels

    /*****
      Device performance *should* theoretically not vary over time
      (unless a site redesign has been performed) and so it makes
      most sense to use a relatively long time period (1 year)
      on which to base adjustments.

      Shorter time periods included for reference, but commented out
    *****/

    //setDeviceBidModifier("LAST_7_DAYS");
    //setDeviceBidModifier("LAST_14_DAYS");
    //setDeviceBidModifier("LAST_30_DAYS");
    //setDeviceBidModifier(LAST_90_DAYS(), TODAY());
    setDeviceBidModifier(LAST_YEAR(), TODAY());

    cleanup(); // Remove Labels
}


//
// Set the Processing label
// This keeps track of which bid adjustments have already been processed
// in the case where multiple time-lookback windows are being used
//
function initLabels() {
    checkLabelExists();
    cleanup();

    var itemsToLabel = [AdWordsApp.campaigns(), AdWordsApp.shoppingCampaigns()];

    for (i = 0; i < itemsToLabel.length; i++) {
        var iterator = itemsToLabel[i].get();

        while (iterator.hasNext()) {
            campaign = iterator.next();
            campaign.applyLabel(LABEL_PROCESSING_DESKTOP);
            campaign.applyLabel(LABEL_PROCESSING_MOBILE);
            campaign.applyLabel(LABEL_PROCESSING_TABLET);
        }
    }
}



//
// Create the processing label if it does not exist
//
function checkLabelExists() {

    var labels = [LABEL_PROCESSING_DESKTOP, LABEL_PROCESSING_MOBILE, LABEL_PROCESSING_TABLET];

    for (i = 0; i < labels.length; i++) {
        var labelIterator = AdWordsApp.labels().withCondition("Name = '" + labels[i] + "'").get();
        if (!labelIterator.hasNext()) {
            AdWordsApp.createLabel(labels[i], "AdWords Scripts label used to process device bid adjustments");
        }
    }
}


//
// Remove Processing label
//
function cleanup() {
    var cleanupList = [AdWordsApp.campaigns(), AdWordsApp.shoppingCampaigns()];

    for (i = 0; i < cleanupList.length; i++) {
        var iterator = cleanupList[i].get();

        while (iterator.hasNext()) {
            campaign = iterator.next();
            campaign.removeLabel(LABEL_PROCESSING_DESKTOP);
            campaign.removeLabel(LABEL_PROCESSING_MOBILE);
            campaign.removeLabel(LABEL_PROCESSING_TABLET);
        }
    }
}


//
// Set Device Bids
//
function setDeviceBidModifier(dateRange, dateRangeEnd) {

    var STANDARD = 0;
    var SHOPPING = 1;

    for (i = 0; i < 2; i++) {
        //Logger.log('---  ' + (i==STANDARD ? 'Standard Campaigns' : 'Shopping Campaigns'));

        var labels = [LABEL_PROCESSING_DESKTOP, LABEL_PROCESSING_MOBILE, LABEL_PROCESSING_TABLET];

        for (l = 0; l < labels.length; l++) {
            //Logger.log('     ' + labels[l]);

            var campaigns = (i==STANDARD ? AdWordsApp.campaigns() : AdWordsApp.shoppingCampaigns());
            var campaignIterator = campaigns.forDateRange(dateRange, dateRangeEnd)
                .withCondition("Status = ENABLED")
                .withCondition("Conversions >= " + MIN_CONVERSIONS)
                .withCondition("LabelNames CONTAINS_ANY ['" + labels[l] + "']")
                .get();

            while (campaignIterator.hasNext()) {
                var campaign = campaignIterator.next();
                var baseConversionRate = campaign.getStatsFor(dateRange, dateRangeEnd).getConversionRate();
                var platforms = [campaign.targeting().platforms().desktop(),
                    campaign.targeting().platforms().mobile(),
                    campaign.targeting().platforms().tablet()
                ];

                //Logger.log('    CAMPAIGN: ' + campaign.getName());

                var targetIterator = platforms[l].get();
                if (targetIterator.hasNext()) {
                    var target = targetIterator.next();
                    var stats = target.getStatsFor(dateRange, dateRangeEnd);
                    var conversions = stats.getConversions();
                    var conversionRate = stats.getConversionRate();
                    var targetModifier = (conversionRate / baseConversionRate);
                    var currentModifier = target.getBidModifier();

                    //Logger.log('    Conversions: ' + conversions);
                    
                    if (conversions >= MIN_CONVERSIONS) {
                        if (Math.abs(currentModifier - targetModifier) >= BID_INCREMENT) {
                            if (targetModifier > currentModifier) {
                                target.setBidModifier(Math.min(currentModifier + BID_INCREMENT, MAX_BID_ADJUSTMENT));
                            } else {
                                target.setBidModifier(Math.max(currentModifier - BID_INCREMENT, 0.1));
                            }
                        }

                        campaign.removeLabel(labels[l]);
                        //Logger.log('    Remove Label: ' + labels[l]);
                    }
                }

            }
        }
    }
}

//
// Date range helper function
// Returns today's date
//
function TODAY() {
    var today = new Date();
    var dd = today.getDate();
    var mm = today.getMonth() + 1; //January is 0!
    var yyyy = today.getFullYear();

    return { year: yyyy, month: mm, day: dd };
}

//
// Date range helper functions
// Returns date 90 days ago
//
function LAST_90_DAYS() {
    var date = new Date(); 
    date.setDate(date.getDate() - 90);
    
    var dd = date.getDate();
    var mm = date.getMonth()+1; //January is 0!
    var yyyy = date.getFullYear();
  
    return {year: yyyy, month: mm, day: dd};
  }

//
// Date range helper functions
// Returns date 1 year ago
//
function LAST_YEAR() {
    var today = TODAY();

    today.year = today.year - 1;
    return today;
}

The latest version of this script is available on GitHub here:
Google Ads Device Bid Adjustment Script

Install the script and have it run once per week.

Every week, the script will look at the past 365 days of data for each of your Search and Shopping campaigns, and make device bid adjustments based on conversion rates.

The script will raise and lower your device bid adjustments by up to 5% each week (you can change this value if you prefer bigger adjustments). You can also adjust the date range for which you want the script to run, and what the minimum number of conversions are required to make a change.

Additional Resources

• Beginner’s Guide to AdWordsGoogle Scripts [WordStream.com]
• How to Automatically Apply Bid Modifiers [SearchEngineLand.com]
• Automated In-Market Audience Bidding [SearchEngineLand.com]
• Bidadjustments for Audiences [AdScripts.com]
• Bidadjustments for Devices [AdScripts.com]