Purchase Order Simulator: Calculate What to Order, How Much, and From Which Supplier

Imperia’s Purchase Order Simulator is an online tool that helps you create a replenishment proposal based on your inventory levels, demand, safety stock, and each supplier’s terms.

It helps you answer some of the most common questions in purchasing planning:

• Which items need replenishment?
• How much should you order for each product?
• Which supplier should each order go to?
• Does the order meet the required minimum quantity?
• Does it meet the minimum order value?

The tool automatically calculates the reorder point for each item, suggests order quantities, and consolidates requirements by supplier, so you can review the order before making a decision.

What Is a Purchase Order Simulator For?

Purchasing planning involves more than identifying products with low inventory.

In a real purchasing scenario, you also need to consider forecast demand, safety stock, lead times, and the commercial terms agreed with each supplier.

An item may need replenishment, but the resulting order may not meet the supplier’s minimum requirement. Similarly, several items that would each generate a small order on their own may form a valid proposal when grouped together.

The Purchase Order Simulator brings these variables together in one analysis.

You can use it to:

• Identify items that need replenishment.
• Automatically calculate reorder points.
• Estimate order quantities.
• Group requirements by supplier.
• Check whether the MOQ is met.
• Validate minimum order values.
• Identify items at risk of a stockout.
• Review the total value of the proposal.
• Compare different replenishment scenarios.
• Export the proposal to continue working with it.

Set Your Supplier Terms

First, define the suppliers you want to include in the analysis.

You can configure up to five suppliers and set three main parameters for each one.

MOQ, or Minimum Order Quantity

MOQ stands for Minimum Order Quantity. It is the minimum number of units a supplier requires to accept an order.

The tool checks this minimum against all the items included in that supplier’s purchase proposal.

For example, if a supplier has an MOQ of 500 units and the calculated requirements for all its items total just 430, the tool will show that you need 70 more units to meet the minimum.

Lead Time

Lead time is the number of days between placing an order and receiving the goods.

This parameter directly affects the reorder point calculation.

A longer supplier lead time means you need to plan replenishment sooner and hold enough inventory to cover demand for a longer period.

Minimum Order Value

Some suppliers set a minimum order value as well as a minimum quantity.

Enter this value so the tool can automatically check whether the consolidated proposal meets the required amount.

This helps you identify cases where the MOQ is met but the order’s total value is still too low.

Add the Items You Want to Manage

Once you’ve set up your suppliers, add the items you want to include in the simulation.

Each item must be linked to one of the suppliers you have already defined.

To calculate the proposal, you’ll need to enter:

• Current inventory.
• Weekly demand.
• Safety stock.
• Unit price.

The tool uses this information, along with the relevant supplier lead time, to calculate replenishment requirements automatically.

Automatically Calculate the Reorder Point

The simulator calculates the reorder point, or ROP, for each item.

The reorder point is the inventory level at which you should place a new purchase order to avoid running out of inventory before the replenishment arrives.

The tool uses the following logic:

Reorder point = Safety stock + Demand during lead time

Demand during lead time is calculated using weekly demand and the supplier’s specified lead time.

For example, an item supplied by a supplier with a 14-day lead time needs enough inventory to cover approximately two weeks of demand before the next replenishment arrives, in addition to the specified safety stock.

When current inventory is at or below the reorder point, the tool marks the item as Order now.

If inventory is still above that level, the item is marked as OK.

Calculate How Much to Order for Each Item

In addition to showing when replenishment is needed, the simulator calculates a suggested order quantity.

The tool aims for an inventory level equivalent to:

4 weeks of demand + Safety stock

It then subtracts the inventory currently available.

In simplified terms:

Order quantity = 4 weeks of demand + Safety stock − Current inventory

If available inventory already covers this target, the tool won’t suggest an additional quantity.

This logic turns inventory and demand data into an initial, actionable replenishment proposal.

Automatically Consolidate Orders by Supplier

Once you’ve added all the items, select Generate order proposal.

The tool automatically groups the line items by assigned supplier.

This lets you move from reviewing individual items to assessing a consolidated purchase proposal.

The overall summary includes metrics such as:

• Number of items that need replenishment.
• Total order value.
• Number of suppliers with active proposals.
• Items with sufficient inventory.

This overview makes it easier to assess the overall scale of your purchasing requirements.

Automatically Check the MOQ

Once the items have been consolidated, the tool adds up the proposed quantities for each supplier and compares the total with its MOQ.

If the total meets the configured minimum, the order is marked as valid against this requirement.

If it falls short, the simulator displays an alert showing how many units are still needed.

For example:

If a supplier’s requirements total 350 units and its MOQ is 500, the tool will show that you need another 150 units to meet the requirement.

This helps you quickly identify orders that address a real replenishment need but cannot yet be placed under the current commercial terms.

Check the Minimum Order Value

The tool applies the same process to each supplier’s minimum order value.

It calculates the value of each line item by multiplying the suggested quantity by its unit price, then adds up all the items for that supplier.

If the total is below the specified minimum order value, an alert shows the difference.

This helps you identify four possible situations:

• Both the MOQ and minimum order value are met.
• The MOQ is met, but the minimum order value is not.
• The minimum order value is met, but the MOQ is not.
• Neither requirement is met.

This information is especially useful when deciding whether to wait, increase the quantity on a line item, or review the proposal before placing the order.

Identify Items at Greater Risk of a Stockout

The simulator also flags items whose inventory has already fallen below their safety stock level.

These cases need special attention because the buffer intended to absorb demand fluctuations or supplier delays has already been used.

This helps you distinguish a routine replenishment requirement from a potentially more critical situation.

Review Each Purchase Proposal

Each supplier has its own results section.

There, you can review the details of every item included:

• Current inventory.
• Reorder point.
• Weekly demand.
• Suggested quantity.
• Unit price.
• Value of each line item.

You can also see:

• Total number of units.
• Total order value.
• Supplier lead time.
• MOQ status.
• Minimum order value status.

This consolidated view helps you assess not only what each item needs, but also whether the proposal is viable for the supplier.

Change the Parameters and Compare Scenarios

One of the simulator’s main uses is to test different situations before making a decision.

You can change parameters such as:

• Weekly demand.
• Available inventory.
• Safety stock.
• Purchase price.
• Lead time.
• MOQ.
• Minimum order value.

For example, you can see what happens if demand for an item increases, a supplier extends its lead time, or you negotiate a lower minimum order quantity.

You can also assess how changing safety stock affects the suggested order quantities.

This turns a snapshot of your inventory into a simple environment for evaluating different scenarios.

Export Your Order Proposal

Once you’ve reviewed the results, you can download the proposal as a CSV file.

The file includes the supplier, item, available inventory, reorder point, weekly demand, suggested quantity, unit price, and line value.

You can continue the analysis in other tools or use the proposal as the basis for your internal purchasing process.

Turn Inventory Data Into a Replenishment Proposal

The challenge in purchasing planning isn’t just knowing how much inventory you have.

The real challenge is turning demand, inventory, and supplier information into specific decisions that account for actual purchasing constraints.

The Purchase Order Simulator connects these variables to create a structured proposal and quickly identify orders that need further review.

As a result, you’ll have a clearer view of:

• Which items need replenishment.
• How much to order.
• Which suppliers account for the requirements.
• Which orders meet the agreed terms.
• Which items are at greater risk.

Use the simulator to test different scenarios and prepare your next purchase orders more effectively.