Merchant math, all of it
Every number your store runs on — calculated free
100+ calculators across pricing, fees, advertising, shipping, inventory and cash flow. Each one shows its formula, handles the platform's real fee structure, and needs no signup.
Advertising & ROAS
Break-even and target math for paid traffic.
- Break-even ROAS Calculator Any platform — the generic version with editable per-order costs.
- Amazon Break-even ACOS Calculator The exact ACOS ceiling for your Sponsored Products campaigns, after referral and FBA fees, not before.
- Shopify Break-even ROAS Calculator The ROAS your Meta and Google campaigns must clear once processing, shipping and fulfillment are paid.
- TikTok Shop Break-even ROAS Calculator Commission plus affiliate cuts eat margin fast at TikTok price points: know your floor before you scale spend.
- Dropshipping Break-even ROAS Calculator Ads are your biggest cost, which makes your break-even ROAS the single number your store lives or dies on.
- Etsy Break-even ROAS Calculator Etsy stacks three separate fees on every sale: your ad break-even starts after all of them.
- Google Ads ROAS Calculator The ROAS your Google Shopping and Search campaigns have to clear before Target ROAS bidding starts spending at a loss.
- Facebook Ads ROAS Calculator The ROAS your Meta campaigns must clear once product, shipping and fees are paid: the floor your ROAS goal should never dip below.
- ROAS Calculator How many dollars of revenue every ad dollar brings back: the first number any paid campaign has to answer for.
- ACOS Calculator The share of every ad-driven sale that went straight back to the ad platform: Amazon PPC's favorite scoreboard.
- Target ROAS Calculator Work the bid target backwards from the profit you want to keep, instead of borrowing a ROAS goal from a blog post.
- CPC Calculator What each visitor from paid traffic actually costs: the unit price of attention.
- CPM Calculator The wholesale price of attention: what a thousand pairs of eyes cost before anyone clicks.
- CPA Calculator The price of one customer: the number your margin has to beat for paid acquisition to make sense.
- CTR Calculator The percentage of people who saw your ad and cared enough to click: the fastest read on whether creative is working.
- TACOS Calculator Ad spend measured against everything you sell: the metric Amazon sellers watch to see whether ads are building a brand or propping one up.
- Ad Budget Calculator Start with the revenue you want and the efficiency you can realistically buy: the budget is just the division.
- PPC Profit Calculator ROAS says the campaign looks good; this says whether each paid order actually puts money in the bank.
- ROAS to ACOS Converter Google speaks ROAS, Amazon speaks ACOS: this translates one campaign scoreboard into the other.
- CPM to CPC Calculator Impressions are what you buy, clicks are what you want: this converts the price of one into the price of the other.
Pricing & Margins
Margins, markups, discounts and break-even points — the math that sets every price.
- Profit Margin Calculator Margin is the share of every sale you actually keep — the number every other decision in your store depends on.
- Markup Calculator Cost-plus pricing done right — and translated into the margin the markup actually produces.
- Selling Price Calculator Start from the margin you need to survive — then let the price be whatever makes that true.
- Discount Calculator The sale price in one step — and a reminder of what the markdown quietly does to your margin.
- Break-even Units Calculator How many sales until the month stops costing you money — the first number a new product or store must know.
- Margin vs Markup Calculator Two percentages, one profit — and an expensive mistake when they get swapped.
- Keystone Pricing Calculator Doubling your cost is retail's oldest pricing rule; see the exact profit and margin it leaves you.
- Wholesale Price Calculator What retailers pay you, and what is actually left per unit after they take their cut of your retail price.
- GMROI Calculator How many gross margin dollars every dollar tied up in inventory earns per year, retail’s favorite buying yardstick.
- Price Increase Calculator Every dollar of a price increase is pure profit: here is exactly how much a raise adds per unit and to your margin.
- Bundle Pricing Calculator Price the bundle so the customer sees a real deal while your blended margin stays healthy.
- Unit Price Calculator The only fair way to compare pack sizes: what one unit actually costs, whatever the box says.
- Gross Profit Calculator What is left after the products pay for themselves: the dollars that fund everything else in the business.
- VAT Price Calculator The tax-inclusive price UK and EU customers must see, computed from your net price in one step.
Marketplace & Payment Fees
What Amazon, Etsy, eBay, Shopify and payment processors really take from each sale.
- Amazon FBA Profit Calculator What one unit actually earns after Amazon takes its referral fee and FBA fulfillment fee.
- Amazon Referral Fee Calculator The commission Amazon takes off the top of every sale, before fulfillment costs even start.
- Etsy Fee Calculator Etsy's three separate fees added up honestly, and the effective percentage they really take.
- eBay Fee Calculator The final value fee plus the per-order charge: what a sale actually leaves in your account.
- PayPal Fee Calculator What PayPal takes from a payment, and the exact amount to invoice so the fee lands on the payer instead.
- Stripe Fee Calculator The 2.9% + 30¢ math on every card charge, and the gross-up trick for when the net amount is what matters.
- Shopify Fee Calculator What Shopify Payments takes from each order, and the effective rate once the 30¢ fixed fee is counted.
- Square Fee Calculator The Square fee on any transaction (online, invoiced, or tapped) and what actually reaches your bank.
- TikTok Shop Fee Calculator TikTok Shop's referral commission on each order, before any affiliate cut you promise creators.
- Walmart Marketplace Fee Calculator Walmart's referral fee on each marketplace sale, with no monthly subscription to amortize, and the WFS fees that stack on top for fulfilled sellers.
- Mercari Fee Calculator Mercari's selling fee and payment processing charge combined into one honest payout number.
- Poshmark Fee Calculator The two-tier Poshmark fee (flat $2.95 under $15, 20% above) resolved into your actual earnings.
- Depop Fee Calculator Depop's fees for selling plus payment processing, and the profit left after what you paid for the item.
- Gumroad Fee Calculator Gumroad's flat cut on each digital sale, and what a price point really pays out.
- Amazon Storage Fee Calculator What Amazon charges every month just to keep your units in the FBA warehouse: the fee that quietly compounds on slow-selling inventory.
- Shopify Profit Calculator What a Shopify order actually leaves in your pocket once product cost, shipping and Shopify Payments are all paid, not just the processing fee.
- Credit Card Processing Fee Calculator The percentage-plus-fixed fee on any card sale, whatever processor runs your checkout.
- Amazon FBA Fee Calculator Every fee Amazon takes from an FBA sale (referral, fulfillment, storage) totalled per unit.
- Amazon Long-Term Storage Fee Calculator The aged-inventory surcharge Amazon adds on top of monthly storage once units sit past 180 days.
- Facebook Marketplace Fee Calculator The selling fee on shipped Marketplace orders, and why local pickup sales keep every dollar.
- GOAT Fee Calculator GOAT's commission, flat seller fee and cash-out charge combined into your real payout.
- StockX Fee Calculator The transaction fee plus payment processing on every StockX sale, resolved into your payout.
- Vinted Fee Calculator Vinted charges sellers nothing: this shows the buyer protection fee your buyer pays on top.
- Grailed Fee Calculator Grailed's tiered commission plus payment processing, resolved into your actual payout.
- Whatnot Fee Calculator The livestream marketplace's commission plus payment processing, per item sold.
- Reverb Fee Calculator The music-gear marketplace's 5% selling fee plus payment processing, on any sale.
- OfferUp Fee Calculator The 12.9% shipped-sale service fee, its $1.99 floor, and the $0 local-sale alternative.
- Depop vs Poshmark Fee Calculator One sale price through both fee stacks: what Depop pays, what Poshmark pays, and the gap between them.
- Depop vs Mercari Fee Calculator Two nearly identical fee stacks with a real crossover price: below it Depop wins, above it Mercari does — barely.
- Poshmark vs Mercari Fee Calculator Resale's highest headline rate against one of its lowest: what the difference costs on your actual price.
- StockX vs GOAT Fee Calculator The two sneaker marketplaces' fee stacks on the same pair: percentage-only against commission-plus-flat-fees.
- OfferUp vs Facebook Marketplace Fee Calculator One shipped sale through both fee stacks: what OfferUp pays, what Facebook Marketplace pays, and the gap.
- Vinted vs Depop Fee Calculator Vinted takes nothing from the seller. Depop takes about 3.3% plus $0.45. The gap is smaller than it used to be.
- Vinted vs Poshmark Fee Calculator Vinted charges the seller nothing. Poshmark takes 20% above $15. The gap is the whole Poshmark commission.
- Mercari vs eBay Fee Calculator One flat rate against a percentage plus a fixed fee. The gap only grows from here.
- Reverb vs eBay Fee Calculator Two places to sell the same guitar, five and a half percentage points apart. Here is what that costs per sale.
- Vinted vs Mercari Fee Calculator Vinted takes nothing from the seller. Mercari takes a flat 10%. The gap is the whole Mercari fee.
- OfferUp vs Mercari Fee Calculator On a shipped sale Mercari wins every time. Hand the item over in a car park and OfferUp charges nothing at all.
- Stripe vs PayPal Fee Calculator Stripe is lower on both the percentage and the fixed fee. That makes the arithmetic short and the decision something else.
Unit Economics
CAC, LTV, AOV and contribution — whether each customer earns more than they cost.
- Customer Acquisition Cost (CAC) Calculator What one new customer actually costs you: the number every ad budget and LTV comparison hangs on.
- Customer Lifetime Value (LTV) Calculator What a customer is really worth over their whole relationship with your store, in margin, not just revenue.
- LTV to CAC Ratio Calculator One ratio that says whether your growth engine builds value or quietly burns it.
- Average Order Value (AOV) Calculator How much the average checkout is worth: the fastest lever for growing revenue without buying more traffic.
- Revenue Per Visitor (RPV) Calculator What each visit to your store is actually worth: conversion rate and order value collapsed into one honest number.
- Contribution Margin Calculator What every single sale contributes toward your fixed costs and profit: the true per-unit scoreboard.
- CAC Payback Period Calculator How long each new customer leaves you out of pocket: the cash-flow truth behind a pretty LTV:CAC ratio.
- Churn Rate Calculator The share of customers slipping out the back door while marketing pours new ones in the front.
- Customer Retention Rate Calculator The percentage of customers who stay: the quiet engine behind every store with strong lifetime value.
- Purchase Frequency Calculator How often the average customer actually comes back: the multiplier hiding inside your lifetime value.
- Customer Lifetime Orders Calculator How many orders (and how many dollars) the average customer relationship produces end to end.
- Refund Rate Calculator The share of orders that come back, and the revenue that quietly leaves with them.
- COGS Calculator What the goods you actually sold this period cost you, straight from three numbers your books already have.
Shipping & Landed Cost
Landed cost, duty and freight — the true per-unit cost of getting goods to the door.
- Landed Cost Calculator The factory price is not your cost: landed cost is what a unit really costs by the time it reaches your warehouse.
- Import Duty Calculator Duty is the tax the border collects on your goods: know it before the invoice does.
- Customs VAT Calculator Import VAT is charged on more than your goods: the taxable base includes freight and duty too.
- Dimensional Weight Calculator Carriers bill the size of your box or the weight of it, whichever costs you more.
- Shipping Cost per Unit Calculator A freight invoice only becomes useful once it is divided into the units it moved.
- Freight Cost Calculator The headline rate per CBM is never the real rate: fixed charges see to that.
- CBM Calculator Cubic meters are the currency of ocean freight: every quote starts with this number.
- Chargeable Weight Calculator Air freight bills the heavier of two weights: the one on the scale and the one your box implies.
- Container Utilization Calculator A container costs the same full or half-empty: utilization tells you which one you booked.
- Shipping Margin Calculator Shipping is a line item with its own P&L, and most stores have never checked whether it is profit or subsidy.
- Free Shipping Threshold Calculator The right free-shipping minimum is not a round number: it is the point where extra order value pays for the label.
- Total Import Cost Calculator One number for the whole shipment: everything the import costs, and what that means per unit.
Inventory
Reorder points, EOQ and turnover — holding enough stock without drowning in it.
- EOQ Calculator The order size where ordering costs and holding costs balance: buy less and you pay in paperwork, buy more and you pay in warehouse space.
- Reorder Point Calculator The stock level that says "order now": early enough that the new shipment lands before the shelf goes empty.
- Safety Stock Calculator The buffer that absorbs a hot sales week or a late container, sized from your real worst case, not a guess.
- Inventory Turnover Calculator How many times a year your inventory converts back into cash: the speed metric behind healthy stock levels.
- Days of Inventory Calculator How many days of selling your current stock represents: the countdown-clock version of inventory turnover.
- Sell-Through Rate Calculator What share of the stock you brought in actually sold: the fastest verdict on a buy, a season, or a product launch.
- Stock to Sales Ratio Calculator How many dollars of inventory you hold for every dollar of monthly sales: the retail buyer’s early-warning gauge.
- Inventory Holding Cost Calculator The rent your inventory quietly pays every month it sits on the shelf: storage, capital, insurance, and shrinkage combined.
- Dead Stock Cost Calculator Dead stock is not just a write-off waiting to happen: it is frozen cash that keeps charging you rent while it waits.
- Fill Rate Calculator The share of orders you could ship immediately from stock: the customer’s-eye view of how good your inventory planning really is.
- Weeks of Supply Calculator The sell-out countdown for a SKU: the number to check against your supplier’s lead time before every reorder.
- Inventory Shrinkage Calculator The gap between what your system says you own and what the shelf count actually finds: theft, damage, and paperwork errors, priced.
- Inventory Aging Calculator Not how old your stock is today — how old it will be when the last unit finally sells, and how much cash rides along the way.
- Inventory Carrying Cost Calculator The all-in price of owning stock, built from its four real components instead of a guessed flat rate.
- Overstock Cost Calculator Every unit beyond your target cover is cash asleep on a shelf — this prices exactly how much.
- Lost Sales Calculator What an empty shelf actually cost: the orders that went to a competitor, net of the customers who waited.
- Stockout Cost Calculator The yearly bill for running out: lost profit plus the rush freight and ad spend it takes to recover.
- EOQ with Safety Stock Calculator The classic order-size formula, made honest: your buffer stock sits under every order cycle and pays holding cost year-round.
- Warehouse Capacity Calculator How many pallets your space can really hold, and how close to the ceiling you are running.
- Warehouse Space Calculator How many square feet your stock really needs once aisles and working space are counted honestly.
- ABC Inventory Calculator The Pareto cut for your catalog: which handful of SKUs carry the business, and which long tail just needs to not run out.
- Demand Forecast Calculator Next season’s unit sales from three things you already know: your run rate, your trend, and how seasonal the month is.
- Retail Inventory Method Calculator A book estimate of what your ending inventory is worth at cost, from numbers you already track — no physical count required.
Conversion & Email
Conversion rates, cart abandonment and email ROI — squeezing more from existing traffic.
- Conversion Rate Calculator The single percentage that tells you whether your traffic problem is actually a website problem.
- Cart Abandonment Cost Calculator Every abandoned cart had a wallet behind it: this is what those walk-aways add up to each month.
- Email ROI Calculator Email is usually the highest-ROI channel a store owns: this puts your own number on that claim.
- Email List Growth Calculator Lists shrink by default: churn eats 20–30% a year, so growth only counts once you subtract the leavers.
- Open Rate Calculator The first gate every email must pass, measured against delivered mail, not the number you sent.
- Email Click Rate Calculator Clicks are the email metric money follows, and click-to-open tells you whether the fault is the subject line or the content.
- A/B Test Significance Calculator Before you ship the winner, check whether your test found a real difference or just measured noise.
- Bounce Rate Revenue Loss Calculator Visitors who leave after one page never see your checkout: here is what that exit door costs in dollars.
- Popup Conversion Calculator Your popup is the front door of your email list: this measures how many visitors actually walk through it.
- Revenue per Email Calculator Opens and clicks are proxies: revenue per email sent is what a send is actually worth.
Store Finance
Cash cycles, runway and growth — the money mechanics behind the storefront.
- Cash Conversion Cycle Calculator How many days each dollar stays trapped between paying suppliers and collecting from customers.
- Working Capital Calculator The cushion between what you own and what you owe over the next twelve months.
- Runway Calculator The one number every founder should know without looking it up: how many months until zero.
- Burn Rate Calculator Turn a bank-balance drop into the monthly and daily rate your business actually spends.
- MRR Growth Calculator Month-over-month MRR growth: the compounding heartbeat of any subscription business.
- Revenue Growth Calculator Compare any two periods on the same footing: the growth rate and the dollar change at once.
- Net Profit Calculator What is actually left after products and overhead both take their share of revenue.
- Operating Margin Calculator How much of every revenue dollar the core business keeps before interest and taxes.
- ROI Calculator One percentage that makes an ad campaign, a bulk inventory buy, and a new tool comparable.
- Break-even Revenue Calculator The revenue line where the month stops losing money, in monthly and per-day terms.
- DSO vs DPO vs DIO Calculator Three day-counts that sound alike and pull in different directions. Here is what each measures and how they combine.
Merchant Tools
Generators and checkers for the daily grind: links, codes, SKUs, slugs, limits.
- UTM Link Builder If the link isn't tagged, the sale has no source — and your best channel looks identical to your worst.
- Discount Code Generator Single-use codes stop coupon-site leakage — but nobody types 500 of them by hand.
- SKU Generator A SKU scheme invented ad hoc at product #5 becomes a warehouse mystery at product #500.
- Product URL Slug Generator The URL is the first thing search engines read about a product page — make it say something.
- Marketplace Character Counter Every marketplace truncates at a different length — and truncation is where clicks go to die.
- Barcode Generator Turn a SKU or product number into a real, scannable barcode — no account, no watermark, nothing uploaded.
SellersCalc is a free suite of 100+ calculators and tools covering every number an online store runs on. Price a product from a target margin, see what Amazon, Etsy or Stripe really keeps from a sale, find the ad spend where campaigns stop losing money, work out the landed cost of an imported unit, your reorder point, your runway, your break-even revenue — then handle the daily grind with the UTM builder, discount-code and SKU generators. Every calculator shows its formula next to its result, runs entirely in your browser, and needs no account.