BJ's Wholesale Club Holdings (BJ -0.04%) investors are in for a volatile trading week. The stock has rallied in 2021, but that surge will be tested when the retailer announces its latest earnings results on Aug. 18.

Expectations are high heading into the report, even though growth is sure to slow compared to a year earlier when people were busy stocking their pantries in the early days of the pandemic. So, let's take a look at the metrics that might keep BJ's running ahead of the market, and of peers like Walmart (NYSE: WMT) and Costco Wholesale (NASDAQ: COST).

An employee stocks fresh vegetables.

Image source: Getty Images.

Market share

BJ's gained more than its fair share of new shoppers during the pandemic, with sales jumping 17% in fiscal 2020, which ends in late January. Its rivals have slightly different fiscal years, but Walmart's Sam's Club grew at a 12% rate over the comparable period. Costco's gains were closer to 14%.

BJ's comparable-store sales and customer traffic numbers will be judged against the latest results from these retailing giants for signs of continued market share growth. Walmart posts its updated numbers two days before BJ's announcement. Costco already revealed solid sales gains for the month of July with comps landing at 8%. Look for CEO Bob Eddy and his team to highlight BJ's two-year growth numbers this week. The warehouse giant's recent expansion pace by that metric landed at 22%.

Passing along higher prices

BJ's said back in May that it was well positioned to weather industry challenges like inflation, supply chain stresses, and slowing growth. The early 2021 profitability pinch was just a temporary swing, management predicted.

BJ Operating Margin (TTM) Chart

BJ Operating Margin (TTM) data by YCharts

Investors can judge that forecast against BJ's profit margins in Wednesday's report. Higher membership fee income should help it keep operating margin at 4% of sales or higher, keeping BJ's in good company compared to industry peers. Success on this score is crucial to fund management's greater ambitions of establishing a national selling footprint over time.

Looking ahead

That growing footprint is a major selling point for the stock. BJ's is planning to open six new warehouses in fiscal 2021, including two in brand-new markets for the retailer. The company currently operates roughly 220 warehouses across 17 states. Costco operates 562 locations across the entire country.

BJ's ability to quickly ramp up toward a national footprint will depend on its ability to keep growing in this competitive niche. While the chain is likely to announce a sharp slowdown this quarter when compared to year earlier, its sales are still running much higher than they were in mid-2019. And BJ's has a bigger cash holding today than it did before the pandemic struck.

These assets should be valuable for the company's next growth phase that involves consolidating recent market share wins while reaching out into new markets that put it in more direct competition with established retailing rivals.