Stop guessing your stock numbers.
Run them.

The toolkit is grouped by the kind of decision you are making. Inventory Metrics covers the core ratios every operator is expected to know: the Inventory Turnover Calculator, the Safety Stock Calculator, the EOQ Optimizer, the Reorder Point Calculator, and the ABC Analysis paired with DSI and the cash conversion cycle. Warehouse Operations covers the physical layer: the Pallet Loading Optimizer, Warehouse Space Utilization, Pick Path Travel Time, and the Cycle Count Frequency Optimizer. Demand and Forecasting covers the uncertain layer: the Demand Variability Index, the Lead-Time Demand Distribution, the Stockout Probability calculator, and the Forecast Bias Tracker, which scores your forecast against its own error with MAPE. Financial Impact translates the physical numbers into money: the Inventory Carrying Cost calculator, the Obsolescence Risk Score, Cash-Flow Working Capital, the GMROI Calculator, and the Shrinkage Loss Estimator. Supplier Management closes the loop with the Supplier Scorecard, the MOQ Break-Even Analyzer, Supplier Lead-Time Variance, and the Total Cost of Ownership calculator. Between them they cover what to order, how much, when to order it, where to put it, what it costs to hold, and whether the supplier behind it is dependable.

The recommended usage follows a fixed sequence rather than the order the tools appear on the page. First establish the health of what you already hold: run the Inventory Turnover Calculator and read the days of stock and the DSI figure out of the ABC Analysis tool, because a business that is stuck with slow-moving stock cannot fix that by ordering differently. Second, size the buffer with the Safety Stock Calculator and the Demand Variability Index, which is where you find out whether your sales history is actually stable enough to plan from. Third, size the order itself with the EOQ Optimizer, then turn that into a calendar with the Reorder Point Calculator. Only after that do the physical and financial tools become useful: the Pallet Loading Optimizer and the Warehouse Space Utilization calculator tell you whether the volume you just ordered physically fits, and the Inventory Carrying Cost and GMROI calculators tell you whether holding it is worth the money. Supplier tools such as the Supplier Scorecard and the MOQ Break-Even Analyzer come last, because a minimum order quantity only becomes meaningful once you know how fast you consume. A useful side effect of this sequence is that each step feeds the next, so the numbers stay consistent instead of being five unrelated figures in a meeting.

Three mistakes are easy to get wrong. The first is treating average sales as stable sales. If you feed a smooth average into the Safety Stock Calculator or the EOQ Optimizer, both will produce a tidy number that assumes every week looks like the last one, and the whole buffer collapses exactly when demand is spiky. The Demand Variability Index exists to expose this, because a coefficient of variation above roughly 0.3 means your history is not steady enough to plan from a mean. The second mistake is ignoring variance in lead time. The Reorder Point Calculator is only as good as the lead time you type in, and if the supplier is usually reliable but occasionally slow, a single average lead time hides the case that actually causes a stockout. The Supplier Lead-Time Variance calculator and the Lead-Time Demand Distribution tool address this directly. The third mistake is underestimating the cost of being out of stock. If you price a stockout at only the margin you lose on the units you did not sell, you will always conclude that carrying more stock is too expensive, which is exactly backwards when the true cost includes an emergency shipment, a lost customer, and a production line that waited. A key point across the whole site: these calculators are order-of-magnitude estimators, and the reliability of the output is bounded by the quality of the input.

The scope is quantitative decision support for small operations, and the limits are worth stating plainly. Every output is an estimate that assumes historical demand continues, that supplier behaviour stays as it has been, and that your inputs are accurate. None of the calculators model seasonality, promotional lifts, or a sudden demand shock, so the Stockout Probability and Demand Variability tools tell you about the past and its spread, not about next quarter. Rates used in the financial calculators, such as carrying cost, capital cost, and shrinkage percentages, are reference values: use the official published figures, the tender document, and your actual contract terms for your situation rather than a default in a form. This is when this stops working: the moment a number here would trigger a real cash decision, a write-down, a supplier change, or a customer commitment, treat the calculator as the draft that starts the conversation and verify every input against your own records, your ERP, and a qualified professional. These tools are not for replacing an ERP, not a substitute for accounting or tax advice, and they do not constitute investment advice or any promise about returns, margins, or supplier performance. They also do not model contract terms such as minimum order quantities, volume rebates, or penalty clauses, and they cannot see a competitor entering your category next month.

Yes, and for some teams that is the better workflow. The value here is speed and sanity: you can test a scenario in two minutes, see the interpretation of the number on the same page, and check whether the assumptions baked into the formula match how your operation actually works. A spreadsheet is better when you need to model many SKUs at once, keep a running history, or link the result to live data. The most useful pattern is to use the calculators to establish the logic and the assumption set for a product family, then carry that logic into a spreadsheet for the full run. The Obsolescence Risk Score and the ABC Analysis tool are good candidates for this, since both need a product-level view. The Warehouse Space Utilization and Pick Path Travel Time calculators work better as one-off checks, because their inputs come from a physical layout that changes less often than a demand forecast does.

Nothing leaves your browser. Every calculation runs client-side, so the sales figures, costs, lead times, pallet dimensions, and supplier names you enter are not transmitted to any server and are not stored by this site. There is no account to create, no email required, and no demo to book. The privacy policy further down this page sets out what the advertising partner can and cannot read, including how to opt out of personalised ads, and the disclaimer section explains what these calculators are not. One caveat worth knowing: some tools keep your inputs in your own browser local storage so that a session survives a page reload, which means clearing site data or switching devices will remove that history. Nothing is shared between devices or accounts, because there are no accounts.