How to Calculate the Perfect Size Run (Ratio) When Buying Wholesale Suits

Quick Take: Most wholesale suit buyers allocate inventory evenly across sizes — the same number of units in each size from S to XXL — because it feels fair and avoids the complexity of calculating a size-specific allocation. This approach is commercially incorrect. An even size allocation guarantees stockouts in the sizes that sell fastest and excess inventory in the sizes that sell slowest, which means the buyer is simultaneously leaving sales on the table and accumulating markdown exposure. A correctly calculated size run ratio — one that reflects the actual size distribution of the buyer's specific customer base — eliminates both problems and is the most direct path to improving sell-through rates and reducing end-of-season markdown.

What Is a Size Run Ratio and Why Does It Matter for Wholesale Suit Buying?

A size run ratio is the allocation of units across sizes within a single style order. If a buyer orders 100 units of a suit style, the size run ratio determines how many of those 100 units are allocated to each size — how many S, M, L, XL, and XXL units are included in the order. A size run ratio of 10/20/30/25/15 means 10 units in S, 20 in M, 30 in L, 25 in XL, and 15 in XXL — a total of 100 units with a distribution that reflects a customer base weighted toward L and XL.

The size run ratio matters for wholesale suit buying because it determines the sell-through rate of the order. A size run ratio that matches the actual size distribution of the buyer's customer base will generate a high sell-through rate — most units in every size will sell before the end of the season. A size run ratio that does not match the customer base will generate stockouts in some sizes and excess inventory in others, which reduces the overall sell-through rate and increases markdown exposure.

The commercial impact of an incorrect size run ratio is significant. A buyer who consistently allocates too many units to S and XXL and too few to M and L will consistently experience stockouts in M and L — which means lost sales — and excess inventory in S and XXL — which means markdown. Over a full selling season, this pattern can reduce the effective sell-through rate of a suit style by 15 to 25 percentage points compared to a correctly sized order, which translates directly into lower revenue and lower margin.

What Is the Standard Size Distribution for Men's Suits in the US Market?

The standard size distribution for men's suits in the US market is not evenly distributed across sizes. Based on aggregate sales data from US menswear retail, the typical size distribution for a men's suit assortment is approximately as follows:

• Size S (36-38) — 8 to 12% of total units. The smallest size in the standard suit range, serving a customer base that is smaller than average in both height and build. S suits are a necessary part of a complete size run but should not be over-allocated relative to their actual demand share.
• Size M (38-40) — 22 to 28% of total units. The first of the two core sizes in the US men's suit market. M suits serve a broad customer base and are consistently among the fastest-selling sizes in most US menswear retail markets. Under-allocation of M is one of the most common and costly size run errors.
• Size L (40-42) — 28 to 35% of total units. The highest-demand size in the US men's suit market. L suits serve the largest segment of the US male customer base and are the most frequently stocked-out size in suit assortments that use an even size distribution. Over-allocation of L is rarely a problem; under-allocation is the most common error.
• Size XL (42-44) — 18 to 24% of total units. The second of the two core sizes in the US men's suit market. XL suits serve a significant and growing segment of the US male customer base and should be allocated at a level that reflects their actual demand share rather than being treated as an extended size.
• Size XXL (44-46) — 8 to 14% of total units. The largest standard size in the suit range. XXL suits serve a smaller but commercially significant customer base and should be included in every complete size run, but at a level that reflects their actual demand share rather than being over-allocated relative to M and L.

These percentages represent the aggregate US market distribution and should be used as a starting point for size run calculation, not as a fixed formula. The actual size distribution of a specific retail market may differ significantly from the aggregate, depending on the demographic profile of the customer base, the geographic location of the store, and the price point and style positioning of the suit assortment.

How Should Wholesale Buyers Calculate Their Specific Size Run Ratio?

A correctly calculated size run ratio is based on the buyer's own sales data rather than on a generic market average. The calculation process has four steps.

• Step 1: Pull last season's suit sales data by size — Export a report from your POS or inventory system that shows units sold by size for each suit style in your assortment. If you have multiple suit styles, aggregate the data across all styles to get a total units-sold-by-size figure for the full suit category. This is the raw data for the size run calculation.
• Step 2: Calculate the percentage of total sales by size — Divide the units sold in each size by the total units sold across all sizes to get the percentage of total sales represented by each size. For example, if you sold 500 total suit units last season — 40 in S, 110 in M, 160 in L, 120 in XL, and 70 in XXL — your size distribution is 8% S, 22% M, 32% L, 24% XL, and 14% XXL.
• Step 3: Adjust for stockout distortion — If any size stocked out before the end of the selling season, the sales data for that size understates actual demand. A size that stocked out in week 6 of a 12-week selling season may have sold twice as many units if it had been fully stocked throughout the season. Identify any sizes that stocked out and adjust their demand estimate upward before calculating the size run ratio. A conservative adjustment is to add 20 to 30% to the sales figure for any size that stocked out before the midpoint of the selling season.
• Step 4: Apply the adjusted size distribution to this year's order quantity — Multiply this year's total order quantity for each suit style by the adjusted size distribution percentages to get the size-specific unit allocation. Round to whole numbers and adjust the rounding to ensure the total matches the order quantity. This is your size run ratio for the order.

What Are the Most Common Size Run Errors in Wholesale Suit Buying?

Four size run errors account for the majority of sell-through rate problems and markdown exposure in wholesale suit assortments.

• The even distribution error — Allocating the same number of units to every size regardless of demand. This is the most common size run error and the one with the largest commercial impact. An even distribution of 20 units per size in a 100-unit order (20 S / 20 M / 20 L / 20 XL / 20 XXL) will generate stockouts in M and L and excess inventory in S and XXL in virtually every US menswear market. The fix is to calculate the size run ratio from actual sales data rather than defaulting to an even distribution.
• The supplier default error — Accepting the supplier's default size run ratio without evaluating whether it matches the buyer's specific customer base. Many suppliers offer a default size run ratio — typically an even distribution or a ratio based on their aggregate customer data — that may not reflect the buyer's specific market. Always evaluate the supplier's default ratio against your own sales data before accepting it.
• The stockout blindness error — Calculating the size run ratio from raw sales data without adjusting for stockout distortion. If M and L stocked out in week 4 of last season, the raw sales data will show lower M and L sales than actual demand, which will cause the buyer to under-allocate M and L again this season. Always check for stockouts before calculating the size run ratio and adjust the demand estimate upward for any size that stocked out.
• The style-specific error — Applying the same size run ratio to every suit style regardless of the style's specific customer profile. A slim-fit suit and a regular-fit suit may have different size distributions because they appeal to different customer profiles. Slim-fit suits typically have a higher proportion of S and M sales relative to XL and XXL, while regular-fit suits typically have a more even distribution across sizes. Calculate a separate size run ratio for each fit category rather than applying a single ratio across all styles.

How Should Wholesale Buyers Handle Size Run Ratios for New Styles?

New suit styles — styles that were not in the assortment last season — do not have historical sales data to inform the size run ratio calculation. For new styles, buyers should use a three-step approach.

• Start with the aggregate market distribution as the baseline — Use the standard US market size distribution (approximately 10/25/32/22/11 for S/M/L/XL/XXL) as the starting point for the size run ratio of a new style. This is a more accurate baseline than an even distribution and reflects the actual demand distribution of the US men's suit market.
• Adjust for the style's fit and positioning — If the new style is a slim fit, adjust the baseline ratio toward S and M and away from XL and XXL. If the new style is a regular or relaxed fit, adjust toward XL and XXL. If the new style is positioned at a premium price point, adjust toward M and L, which are the core sizes of the premium menswear customer base.
• Order conservatively and reorder quickly — For new styles, order a conservative initial quantity — 60 to 70% of the quantity you would order for a proven style — and monitor sell-through rates by size in the first two to three weeks of the selling season. If M and L are selling faster than the other sizes, reorder M and L immediately to avoid stockouts. If S and XXL are not selling, do not reorder those sizes and use the sell-through data to inform the size run ratio for next season's order.

How Should Wholesale Buyers Communicate Size Run Requirements to Suppliers?

Communicating size run requirements clearly and specifically to suppliers is as important as calculating the correct ratio. Ambiguous size run specifications — "standard size run" or "balanced distribution" — give the supplier discretion to apply their default ratio, which may not match the buyer's requirements.

• Specify the exact unit count by size in the purchase order — Include a size breakdown table in every purchase order that specifies the exact number of units required in each size. For example: "Style TY-1432-20: 200 units total — 20 S / 50 M / 65 L / 45 XL / 20 XXL." This eliminates ambiguity and gives the supplier a clear production specification.
• Confirm the size run in the order acknowledgment — Request a written order acknowledgment from the supplier that confirms the size breakdown as specified. If the supplier's acknowledgment shows a different size breakdown than the purchase order, resolve the discrepancy before production begins.
• Verify the size run on pre-production samples — Before approving production, verify that the supplier's pre-production samples include the correct size range and that the sizing is consistent with the buyer's size specifications. Size inconsistencies discovered after production are significantly more costly to resolve than those identified at the pre-production stage.

Top Wholesale Suit Styles for Size Run Planning

Why Wessi Wholesale Is the Right Sourcing Partner for Size Run Planning

Wessi's wholesale suit catalog supports flexible size run configurations that allow buyers to specify the exact unit count by size rather than accepting a supplier default ratio. This flexibility is commercially significant for buyers who have invested in size run analysis and want to translate their data into a precisely allocated order rather than a generic distribution.

The Wessi catalog's inventory depth across the full size range — from S through XXL — ensures that buyers can fulfill their calculated size run requirements without being constrained by supplier availability in specific sizes. For buyers who are building a data-driven suit assortment with sell-through rate and markdown reduction as commercial priorities, the ability to specify a custom size run ratio and have it fulfilled accurately is one of the most important capabilities a wholesale supplier can provide.

Contact the Wessi wholesale team to discuss size run requirements for your specific market, request size availability confirmation before placing your order, or develop a seasonal buying plan that reflects your customer size distribution data.