To estimate the costs of migrating an on-premises application like App1 to Azure, the Azure Total Cost of Ownership (TCO) Calculator is the most appropriate tool. It is specifically designed to help users compare the cost of running their existing on-premises workloads against the cost of running those same workloads in Azure, providing a detailed report on potential savings.

To minimize compute costs for a migrated application, particularly one running on Windows Server or using SQL Server, the Azure Hybrid Benefit is a primary cost-saving measure. This benefit allows you to use your existing on-premises licenses with Software Assurance on Azure, which can significantly reduce the costs of running virtual machines and databases by eliminating the software licensing fees from the Azure bill.

Microsoft Azure Documentation, "Azure TCO Calculator". The documentation states, "The Total Cost of Ownership (TCO) Calculator helps you to estimate the cost savings you can realize by migrating your workloads to Azure." This confirms its role as a pre-migration estimation tool.

Microsoft Azure Documentation, "What is Azure Hybrid Benefit?". The official documentation explains, "Azure Hybrid Benefit is a licensing benefit that helps you to significantly reduce the costs of running your workloads in the cloud. It works by letting you use your on-premises Software Assurance-enabled Windows Server and SQL Server licenses on Azure." This directly supports its use for minimizing migration costs.

Microsoft Azure Documentation, "Azure Advisor for cost optimization". Advisor provides recommendations to optimize costs for existing Azure resources, stating it "helps you optimize and reduce your overall Azure spend." It is not a tool for estimating costs for a new workload.

Microsoft Learn, "SC-100: Design a security posture management strategy", Module 2, Unit 5. This module discusses how compliance and security requirements often mandate predictable and stable infrastructure. This implicitly discourages the use of interruptible compute like Azure Spot VMs for such workloads, as their eviction model can conflict with availability requirements mandated by compliance standards.