Stock Control: The Key Inventory Formulas Every Business Needs
Stock control made simple: the safety stock, reorder point, average stock and minimum stock formulas every e-commerce and B2B business needs, with worked examples.
By The Juvo team — 11 August 2026
TL;DR: Stock control comes down to a handful of formulas that tell you how much to hold and when to reorder. This guide covers the five that matter most: safety stock, reorder point, average stock, minimum stock and stock coverage. Get them right and you avoid both empty shelves and cash tied up in stock, whether you sell online or supply other businesses.
Holding stock is a balancing act. Too little and you miss sales or break a delivery promise. Too much and your cash sits on a shelf gathering dust. The good news is that stock control is not guesswork. A few simple formulas do the heavy lifting, and they work the same whether you run an online shop or supply trade customers. This guide is the map. Each formula below links to a deeper walkthrough with worked examples.
Why do stock formulas matter?
Stock formulas turn guesswork into numbers. They tell you the smallest amount of stock that keeps orders flowing without tying up cash you don’t need. For an online store that means fewer “out of stock” pages. For a business supplying other companies it means fewer missed delivery dates. Used together, these numbers balance the main cost drivers in inventory: the cost of running out, and the cost of holding too much.
What is safety stock and how do you calculate it?
Safety stock is the buffer you keep to cover surprises, like a sudden demand spike or a late supplier. A widely used formula is (maximum daily sales x maximum lead time) minus (average daily sales x average lead time). Say you usually sell 50 units a day with a 4-day lead time, but on busy days you sell 80 with a 7-day wait. Your safety stock is (80 x 7) − (50 x 4), which is 360 units. That is your cushion before you hit zero. We break this down step by step in our dedicated safety stock guide.
Reorder point: when should you place the next order?
The reorder point is lead time demand plus safety stock, where lead time demand is your average daily sales multiplied by your lead time. When stock drops to this number, it is time to order. The reorder point tells you when to buy, while safety stock is the buffer you try never to touch. A store selling 20 birthday cards a day with a 5-day lead time and 40 units of safety stock reorders at 140 units. Our reorder point guide works through more examples.
How do you work out average stock?
Average stock is simply your opening stock plus your closing stock, divided by two, across a chosen period. It feeds two useful figures: stock coverage, which tells you how many days of sales you hold, and inventory turnover, which shows how fast stock sells and clears. Watching average stock stops slow movers quietly building up. Our average stock guide shows how to use it to spot problems early.
Minimum stock, safety stock and reorder point: what’s the difference?
These three get muddled all the time. Minimum stock is the floor you never want to drop below. Safety stock is the buffer that sits just under your reorder point. The reorder point is the trigger that starts the next order. Keeping them separate stops you double-counting the same units and over-ordering. Our minimum stock guide explains how to set each one.
Where a 3PL fits in
When you outsource fulfilment, your logistics provider tracks these levels for you and flags reorders, so the formulas run quietly in the background. This works the same for an online brand shipping single parcels and a business sending pallets to trade customers. At Juvo, real-time stock visibility sits inside our storage and stock management service, backed by a client portal that lets you see levels and anticipate replenishment.
Good stock control is not about buying software or learning maths. It is about knowing five numbers and acting on them. Start with safety stock and the reorder point, since those two prevent most stockouts, then layer in average stock and coverage to trim the excess. If you would rather your provider run the numbers for you, talk to our team about how we manage stock for e-commerce and B2B clients alike.
Frequently Asked Questions
What are the most important stock control formulas? The five that matter most are safety stock, reorder point, average stock, minimum stock and stock coverage. Safety stock and the reorder point prevent stockouts, while average stock and coverage help you spot and trim excess inventory.
What is the safety stock formula? A common version is (maximum daily sales x maximum lead time) minus (average daily sales x average lead time). It sizes the buffer you need to cover demand spikes and supplier delays.
How is the reorder point calculated? The reorder point equals lead time demand plus safety stock. Lead time demand is your average daily sales multiplied by your lead time. When stock falls to this level, you place the next order.
What is the difference between minimum stock and safety stock? Minimum stock is the absolute floor you never want to fall below. Safety stock is the buffer that sits just under your reorder point to absorb surprises. They are related but not the same number.
Can a 3PL manage stock levels for me? Yes. A third-party logistics provider can track your stock levels, flag when to reorder and give you real-time visibility through a client portal, for both e-commerce and B2B operations.