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“Sales grew 27%” alone says little: if prices rose 20%, much of the growth is only inflation, not more customers. This tool separates nominal from real growth and, if you have sales quantity, shows how many toman of the sales change came from “price” and how many from “volume”.

With a product file it goes one level deeper: price and volume effects per product and, at aggregate level, "mix effect"—whether sales shifted toward more or less expensive products. The sum of all effects always equals total sales change exactly.

• Nominal growth = (period 2 sales − period 1 sales) ÷ period 1 sales. When period 1 sales are zero, the percentage is undefined and only the absolute change is shown.
• Real growth uses only an index you enter: inflation = index 2 ÷ index 1 − 1; real growth = (1 + nominal growth) ÷ (1 + inflation) − 1; period 2 sales at period 1 prices = sales 2 × index 1 ÷ index 2. The tool assumes no inflation rate on its own.
• Price per period = sales ÷ quantity in that period — the weighted-average price you actually received, not the list price. If you lack quantity but have unit price, quantity = sales ÷ price. If you gave both and your price differs from sales ÷ quantity by more than 1%, you get a warning and the calculation uses sales ÷ quantity.
• Symmetric method: volume effect = Δqty × (price 1 + price 2) ÷ 2 and price effect = Δprice × (qty 1 + qty 2) ÷ 2. The interaction term (Δprice × Δqty) is split evenly between the two effects — the Shapley split for two factors.
• Laspeyres method: volume effect = Δquantity × price 1 (volume at old prices), price effect = Δprice × quantity 1 (price at old quantities), and interaction effect = Δprice × Δquantity on a separate line.
• In both methods, effect totals exactly equal sales change: amounts round to two decimals and the last line absorbs rounding remainder.
• Products file: the same decomposition runs for each product. A product present in only one period takes that period’s price for the other; so its entire change is a “volume effect” (from or to zero) and its price effect is zero. A product with revenue in a period but zero quantity is not decomposed and its change goes in the “interaction/remainder” column.
• Mix effect (file only): total volume effect = (total count 2 − total count 1) × average price of all units (Laspeyres: period 1 average; symmetric: average of both periods). Mix effect = sum of product volume effects − total volume effect—the part of change not explained by each product's price and volume, from shifting sales between expensive and cheap products. Positive mix means sales shifted toward more expensive products. Total volume effect + mix effect + price effect (+ interaction) = total sales change.
• Annualised growth (using month gap only) = (sales 2 ÷ sales 1)^(12 ÷ months) − 1; for comparing periods of different length.

• The two periods must be the same length and definition (both gross or both net of discount and returns); comparing a month with a quarter, or a holiday month with a normal month, makes growth misleading.
• “Real growth” is only as good as the index you chose; CPI is not necessarily your product’s market inflation. Always keep index source and period beside the result.
• "Price" in this tool is the weighted average of revenue ÷ quantity; if a product's size or pack mix changed, part of the "price effect" is really within-product mix. To see mix, split the products in the file.
• The two decomposition methods give two different answers and neither is “more correct”; state the method in the report and do not switch between periods.
• Sales growth is not profit growth: with cost inflation, sales may grow while profit shrinks. For profit per order, see the true order profit tool.
• This tool is a calculator, not a forecast and not advice: no figure is pricing or investment advice.