Direct Labor Hours
Machine Hours
Direct Labor Cost ($)
Units of Production
Please enter a value greater than 0.
Predetermined Overhead Rate:
$0.00
per direct labor hour
function calculatePOR() {
// 1. Get input values using var
var overheadInput = document.getElementById("estOverheadCost");
var baseInput = document.getElementById("estBaseAmount");
var typeSelect = document.getElementById("allocationBaseType");
var overheadCost = parseFloat(overheadInput.value);
var baseAmount = parseFloat(baseInput.value);
var baseType = typeSelect.value;
var resultBox = document.getElementById("porResult");
var resultValue = document.getElementById("resultValue");
var resultExplanation = document.getElementById("resultExplanation");
var baseError = document.getElementById("baseError");
// 2. Reset errors
baseError.style.display = "none";
resultBox.style.display = "none";
// 3. Validation logic
if (isNaN(overheadCost) || overheadCost < 0) {
alert("Please enter a valid Estimated Overhead Cost.");
return;
}
if (isNaN(baseAmount) || baseAmount <= 0) {
baseError.style.display = "block";
return;
}
// 4. Calculate Predetermined Overhead Rate (POR)
// Formula: Estimated Overhead / Estimated Allocation Base
var rate = overheadCost / baseAmount;
// 5. Formatting Output based on selection
var formattedRate = "";
var suffix = "";
if (baseType === "direct_labor_cost") {
// If base is dollars, usually expressed as a percentage or $ per $
// Option A: Percentage
var percentage = (rate * 100).toFixed(2);
formattedRate = percentage + "%";
suffix = "of Direct Labor Cost";
} else {
// For hours or units, expressed as Currency per Unit
formattedRate = "$" + rate.toFixed(2);
if (baseType === "direct_labor_hours") {
suffix = "per Direct Labor Hour";
} else if (baseType === "machine_hours") {
suffix = "per Machine Hour";
} else if (baseType === "units_produced") {
suffix = "per Unit Produced";
}
}
// 6. Display Result
resultValue.innerHTML = formattedRate;
resultExplanation.innerHTML = suffix;
resultBox.style.display = "block";
}
How Is the Predetermined Overhead Rate Calculated?
In managerial accounting and cost accounting, accuracy in product pricing relies heavily on how well a company allocates its indirect costs. Unlike direct materials and direct labor, which can be traced easily to a specific product, manufacturing overhead consists of indirect costs (like factory rent, electricity, and supervisor salaries) that must be allocated. This is where the Predetermined Overhead Rate (POR) becomes an essential tool.
The predetermined overhead rate is calculated at the beginning of an accounting period to apply estimated overhead costs to cost objects (such as products or job orders) during the period.
The Golden Formula:
Predetermined Overhead Rate = Estimated Total Manufacturing Overhead Cost / Estimated Total Amount of Allocation Base
Step-by-Step Calculation Guide
To calculate the rate correctly, you must follow these specific steps before the financial period begins:
Estimate Total Manufacturing Overhead: Sum up all budgeted indirect costs for the upcoming year. This includes factory utilities, depreciation on equipment, property taxes on the factory, and indirect labor.
Select an Allocation Base: Choose a cost driver that causes the overhead to increase. This connects the overhead cost to the production volume.
Estimate the Total Allocation Base: Project how much of that base (activity level) will be used during the year.
Divide: Divide the estimated costs (Step 1) by the estimated base (Step 3).
Choosing the Right Allocation Base
The accuracy of your predetermined overhead rate depends significantly on the allocation base chosen. The most common bases used in manufacturing include:
Direct Labor Hours: Best used when production is labor-intensive and manual work drives overhead costs.
Machine Hours: Ideal for highly automated factories where machinery maintenance and depreciation are the primary overhead drivers.
Direct Labor Cost: Used when higher-paid employees correlate with higher overhead usage, often expressed as a percentage.
Units of Production: Useful only if a company produces a single, uniform product.
Calculation Example
Let's assume "Precision Manufacturing Inc." is preparing its budget for the upcoming year. They estimate the following:
Total Estimated Overhead Costs: $600,000 (Rent, Utilities, Insurance)
Primary Cost Driver: Machine Hours
Estimated Total Machine Hours: 40,000 hours
Using the calculator above or the formula manually:
$600,000 / 40,000 hours = $15.00 per machine hour
This means for every hour a machine runs to produce a widget, the company adds $15.00 to the cost of that widget to account for overhead.
Why Not Use Actual Overhead Rates?
You might wonder, why estimate? Why not wait until the end of the year to use the actual costs? The problem is timing. Managers need cost data immediately to price jobs, bid on contracts, and evaluate profitability throughout the year. Waiting until the year ends to determine the actual overhead rate would delay financial reporting and decision-making. The POR allows for "Normal Costing," which smooths out seasonal fluctuations in overhead costs.
Handling Overapplied or Underapplied Overhead
Because the POR is based on estimates, the amount of overhead applied to products will rarely equal the actual overhead costs incurred by the end of the year.
Underapplied Overhead: Actual costs were higher than applied costs (production costs were understated).
Overapplied Overhead: Applied costs were higher than actual costs (production costs were overstated).
At the end of the period, this variance is usually adjusted against the Cost of Goods Sold (COGS) account.