In supply chain management and logistics, the Fill Rate is a critical Key Performance Indicator (KPI) that measures the percentage of customer demand met through immediate stock availability. It helps businesses understand how effectively they are fulfilling orders without resorting to backorders or losing sales due to stockouts.
Whether you are calculating Line Fill Rate, Case Fill Rate, or Order Fill Rate, the core concept remains the relationship between what was ordered and what was successfully shipped.
Inventory Fill Rate Calculator
Fill Rate Percentage:–
Unfilled Demand (Backorders/Lost):–
Performance Status:–
function calculateFillRate() {
// 1. Get input values
var demandInput = document.getElementById('totalDemand');
var shippedInput = document.getElementById('totalShipped');
var errorDiv = document.getElementById('error-message');
var resultBox = document.getElementById('result-box');
var demand = parseFloat(demandInput.value);
var shipped = parseFloat(shippedInput.value);
// 2. Validate inputs
if (isNaN(demand) || isNaN(shipped)) {
errorDiv.style.display = 'block';
errorDiv.innerHTML = "Please enter valid numbers for both fields.";
resultBox.style.display = 'none';
return;
}
if (demand <= 0) {
errorDiv.style.display = 'block';
errorDiv.innerHTML = "Total Demand must be greater than 0.";
resultBox.style.display = 'none';
return;
}
if (shipped demand) {
// While technically possible in data errors or substitutions, for fill rate calculation
// we usually cap at 100% or warn the user. We will show >100% but add a note.
errorDiv.style.display = 'block';
errorDiv.style.color = '#e67e22'; // Orange warning
errorDiv.innerHTML = "Note: Shipped units exceed demand. Ensure this isn't a data entry error.";
} else {
errorDiv.style.display = 'none';
}
// 3. Perform Calculation
var fillRate = (shipped / demand) * 100;
var missed = demand – shipped;
// Handle negative missed demand if shipped > demand
if (missed = 98) {
status = "Excellent";
statusColor = "#27ae60"; // Green
} else if (fillRate >= 95) {
status = "Good";
statusColor = "#2980b9"; // Blue
} else if (fillRate >= 90) {
status = "Average";
statusColor = "#f39c12"; // Orange
} else {
status = "Needs Improvement";
statusColor = "#c0392b"; // Red
}
// 5. Update UI
document.getElementById('fillRateResult').innerHTML = fillRate.toFixed(2) + "%";
document.getElementById('missedDemandResult').innerHTML = missed.toLocaleString() + " Units";
var statusElement = document.getElementById('statusResult');
statusElement.innerHTML = status;
statusElement.style.color = statusColor;
resultBox.style.display = 'block';
}
The Fill Rate Formula
To calculate the fill rate, you divide the number of units shipped by the number of units ordered, then multiply by 100 to get a percentage.
Fill Rate % = ( Total Items Shipped / Total Items Ordered ) × 100
Example Calculation
Imagine a retailer places an order for 1,000 units of a specific product. However, your warehouse only has 940 units in stock, which are shipped immediately. The remaining 60 units are placed on backorder.
Total Demand: 1,000 Units
Total Shipped: 940 Units
Calculation: (940 / 1000) × 100 = 94%
In this scenario, your fill rate is 94%, meaning you failed to meet 6% of the immediate demand.
Why Is Fill Rate Important?
Fill rate is a direct indicator of customer satisfaction and inventory efficiency. A low fill rate suggests that customers are not getting what they want when they want it, which can lead to:
Lost Sales: Customers may cancel orders or buy from competitors.
Increased Costs: Handling backorders requires extra administrative work and split shipments (double shipping costs).