Analyze inventory velocity and forecast stock duration.
Daily Rate of Sale:–
Weekly Rate of Sale (WROS):–
Monthly Projection (30 Days):–
Estimated Days Until Stockout:–
function calculateRateOfSale() {
var unitsSold = parseFloat(document.getElementById('unitsSold').value);
var timePeriod = parseFloat(document.getElementById('timePeriod').value);
var currentInventory = parseFloat(document.getElementById('currentInventory').value);
// Validation
if (isNaN(unitsSold) || isNaN(timePeriod) || timePeriod 0) {
daysSupply = currentInventory / dailyRate;
if (currentInventory <= 0) {
supplyText = "Out of Stock";
} else {
supplyText = daysSupply.toFixed(0) + " Days";
}
} else {
supplyText = "No Sales Activity";
}
// Update DOM
document.getElementById('dailyRateResult').innerHTML = dailyRate.toFixed(2) + " units/day";
document.getElementById('weeklyRateResult').innerHTML = weeklyRate.toFixed(2) + " units/week";
document.getElementById('monthlyRateResult').innerHTML = monthlyRate.toFixed(0) + " units/month";
document.getElementById('daysSupplyResult').innerHTML = supplyText;
document.getElementById('rosResults').style.display = 'block';
}
How Do You Calculate Rate of Sale?
Rate of Sale (ROS) is a critical Key Performance Indicator (KPI) in retail and supply chain management. It measures the velocity at which a product is sold over a specific period of time. Understanding your rate of sale helps businesses optimize inventory levels, plan reorders, and identify best-selling or underperforming products.
The Rate of Sale Formula
The basic formula for calculating the Rate of Sale is straightforward: divide the total number of units sold by the number of days in the time period analyzed.
Formula:
Rate of Sale (ROS) = Total Units Sold ÷ Number of Days
While the daily rate is the base metric, retailers often convert this to a Weekly Rate of Sale (WROS) to smooth out daily fluctuations (like weekend spikes). To find the WROS, simply multiply the daily rate by 7.
Why is Calculating Rate of Sale Important?
Inventory Management: Helps prevent stockouts by predicting how long current inventory will last (Days of Supply).
Performance Analysis: Allows for the comparison of product performance across different categories or store locations regardless of the total volume.
Purchasing Decisions: Provides data-driven insights on how much stock to order to cover a specific lead time.
Example Calculation
Imagine you run a boutique and want to analyze the sales of a specific denim jacket.
Units Sold: 45 jackets
Time Period: 30 days (last month)
Current Inventory: 60 jackets
Step 1: Calculate Daily ROS
45 units ÷ 30 days = 1.5 units per day
Step 2: Calculate Weekly ROS
1.5 units/day × 7 days = 10.5 units per week
Step 3: Estimate Stock Duration
60 units (inventory) ÷ 1.5 units/day = 40 days of supply remaining
In this example, the retailer knows they have roughly 40 days before they run out of denim jackets, assuming the rate of sale remains constant. This allows them to plan their reorder point effectively.