Why Is Size ۱۸ the Most Widely Used Rebar Size in the Market?

If your warehouse is limited and you have to decide which rebar size to always keep in stock, the answer for most Iranian markets is one number: size ۱۸. This size is neither so light that it is insufficient for primary structures nor so heavy that it is purchased only for special projects; this balance has made it the default option for ordinary building frames.

Why Exactly Size ۱۸, Not ۱۶ or ۲۰

The frames of most ordinary residential and commercial buildings in Iran fall, in terms of load and span, precisely within the range for which size ۱۸ is sufficient and economical. Size ۱۶ is suitable for lower loads, and size ۲۰ for higher loads or larger spans; however, the largest number of actual market projects have exactly the moderate loads for which ۱۸ is designed.

If you have to always keep only one size in stock, it will probably be size ۱۸.

What This Pattern Means for Your Inventory Management

• Keep a larger volume of size ۱۸ in stock than other sizes to lose fewer customers.
• Purchase less widely used sizes (such as ۱۲ or ۲۴) based on a specific order or regular customer, rather than maintaining a large inventory of them.
• If your inventory budget is limited, balancing sizes ۱۶, ۱۸, and ۲۰ usually provides the greatest coverage of actual demand.

The Risk of Storing the Wrong Inventory

Stocking a large volume of a less widely used size such as ۲۴, even at a good purchase price, can tie up your capital for a long time because there are fewer actual customers for that size. Conversely, insufficient stock of size ۱۸ during the peak construction-demand season means losing a customer who could have finalized their purchase that same day.

How to Adjust This Pattern for Your Region

This demand distribution is a general market rule, not a fixed law for every location. If your customers are more involved in industrial or shed projects, the share of larger sizes such as ۲۰ and ۲۲ in your inventory should be greater. The best approach is to record your actual sales for several months and see which sizes are genuinely reordered more often, rather than relying solely on a general market pattern.