5 Numbers Every eCommerce Seller Needs to Know Every Month

Most ecommerce sellers check revenue once a month and call it financial management.

Revenue is a starting point. What actually moves the needle—payroll, reinvestment, whether you're building a real business or burning cash—comes down to five numbers that separate successful sellers from those running in circles.

1. Net Revenue Per Channel (Not Gross GMV)

Gross merchandise value tells you nothing about what you keep. If you sold $100,000 on Amazon, but paid Amazon 15% in fees, your seller fees, your cost of goods, your payment processing—you're keeping maybe $40,000 to $55,000. That range matters.

Net revenue per channel is what you actually earned after platform fees, payment processing fees, and COGS. Calculate it for every sales channel: Amazon, Shopify, your own website, TikTok Shop, wherever you sell.

Why it matters: You can't compare channel performance or decide where to scale without knowing which channels are actually profitable. A high-revenue channel can be a cash sinkhole if fees and COGS eat the margin.

Just Pull the Formula

• Gross revenue by channel (from your accounting software or dashboard)
• Minus platform fees (Amazon FBA, marketplace commissions, payment processing)
• Minus COGS for units sold on that channel
• Equals net revenue per channel

Do this monthly. Channel profitability shifts overnight during Q4 or seasonal spikes. You can't wait for quarterly review.

2. COGS as a Percent of Net Revenue

If your COGS was $30,000 and your net revenue was $100,000, your COGS ratio is 30%. That's the ratio that actually tells you whether your margins are tightening or holding steady.

eCommerce sellers often fixate on product cost per unit. That's procurement; it's not the full picture. When you layer in tariffs, freight, currency fluctuations, duty fees, and shrinkage, your effective COGS shifts. The ratio catches that shift month to month.

Why it matters: A climbing COGS ratio signals that your supply chain costs are outpacing revenue growth. You need to either raise prices, negotiate supplier costs, or accept shrinking margins. Knowing the direction early prevents a profit collapse.

The 60/30/10 Framework

• 60% range: COGS at or below 40%, leaving 60% gross profit. Healthy for most product categories.
• 30% range: COGS climbing toward 45-50%. Margins are tightening. Time to audit suppliers or adjust pricing.
• 10% range: COGS above 50%. You're not profitable at scale. Fix it or exit the product.

3. Monthly Advertising Spend as a Percent of Revenue

Most ecommerce sellers track ad spend. Almost none compare it to revenue—and that blindness costs them.

If you spent $10,000 on ads and generated $100,000 in revenue, your ad spend ratio is 10%. If the same $10,000 generated $80,000 in revenue, your ratio is 12.5%. That shift from 10% to 12.5% is the difference between a healthy payoff and bleeding cash on inefficient channels.

Why it matters: This is the metric sellers track last—and the first one to warn you that customer acquisition cost is rising. When the ratio climbs above your threshold, you pause immediately. You don't wait until month-end to discover you burned $15,000 on a channel that turned unprofitable halfway through.

Your Benchmarks Are Probably Wrong

• Amazon PPC: 8-15% of channel revenue is healthy
• Shopify/independent: 15-25% depending on product price point
• Facebook/Instagram: 20-40% for new products; 10-20% for winners

Most sellers use industry averages. You need YOUR threshold. If you're above it, pause immediately and diagnose: wrong audience, wrong creative, wrong product for paid ads, or all three.

4. Inventory Turnover Rate

Inventory turnover is COGS divided by average inventory value. If your COGS is $120,000 per year and your average inventory sits at $40,000, your turnover is 3x per year. That means cash is locked in product for roughly four months before it sells.

Fast-moving inventory (6x to 12x per year) means cash cycles through quickly. Slow-moving inventory (under 2x per year) means capital is tied up, you're carrying storage costs, and you risk markdowns on stale product.

Why it matters: A low turnover rate signals dead inventory consuming warehouse space and cash. Improving turnover by even 1x per year frees up tens of thousands in working capital—money you can use for payroll, new products, or ad spend instead of storing last season's stock.

The Calculation (It's Simple)

• COGS from the past 12 months
• Average inventory value: (beginning balance + ending balance) ÷ 2
• Divide COGS by average inventory = turnover rate
• Track monthly and flag any downward trend immediately

Improving this metric is the fastest way to unlock working capital. That capital pays your team, funds new inventory, or covers unexpected costs. Dead inventory does none of those things.

5. Net Operating Cash Flow (The Number That Actually Matters)

Profit and cash flow are not the same thing. You can report a $50,000 net profit and still run out of money.

Net operating cash flow is cash generated from normal business operations, minus operating expenses, before financing and investment. It's what you actually have in the bank to pay payroll, reorder inventory, or cover unexpected costs.

If your P&L shows $50,000 profit but your cash balance dropped by $20,000, something is pulling cash out: overstocking inventory, extending customer payment terms, taking on supplier debt, or timing misalignment between when you pay suppliers and when customers pay you.

Why it matters: This is the number that determines payroll viability. You can't pay yourself with accrual-based profit. You pay yourself with cash.

The Math (This Matters More Than You Think)

• Net profit (from your P&L)
• Plus non-cash expenses (depreciation, amortization)
• Minus increases in inventory or accounts receivable
• Plus increases in payables
• Equals operating cash flow

If operating cash flow is lower than your profit, you're deferring the problem. If it's negative, you're burning cash and didn't know it. Fix it or the business folds—regardless of what your P&L says.

Connect These Five Numbers

Track these five monthly. Not quarterly. Not when something feels off. Every month, the same day.

Net revenue per channel tells you which channels to scale. COGS ratio tells you if margins are slipping. Ad spend ratio warns you early when acquisition cost climbs. Inventory turnover frees cash. Net operating cash flow tells you what you actually have left to run the business.

Together, they paint a complete picture of a seller's financial health—not the illusion of it.

Stop Calculating This Yourself

These five metrics separate sellers who scale from sellers who stagnate. But calculating them manually every month is a tax on your time—time you should spend on revenue and inventory, not spreadsheets.

ECOM CPA (4.8 rating, based in Grants Pass, OR) specializes in exactly this problem. They automate the setup, run the monthly calculations, and deliver a cash flow forecast that tells you what you actually have to work with. They've built their practice around high-volume sellers on Amazon, Shopify, and multi-channel operations, and they understand the fee structures, payment timing, and working capital timing issues that most CPAs miss.

Let ECOM CPA build the infrastructure, then you focus on scaling. Your numbers should move as fast as your inventory.

Your business moves at the speed of data. Make sure your data is moving.