Type in your habits. Get a number back. Then sit down, because the number is usually bigger than you expected.
A fee audit calculator SaaS makes one promise: tell it what you do, and it tells you what you pay. For investors who have never added up their broker's fees, the result is usually a small shock. That shock is the product working.
Here is how the honest ones work. You enter your activity: trades per month, options contracts, margin balance, wires per year, paper statements or not. The calculator prices that activity against published fee schedules and shows your estimated annual cost per broker. Key word: estimated. It is only as accurate as your inputs. Be honest about how much you actually trade, not how much you aspire to trade.
What to check before trusting one. First, the data date. Fee schedules change, and a calculator running on last year's PDFs is a history lesson. Look for a last-updated stamp. Second, whether it covers your specific fees. A calculator that ignores exercise and assignment fees is useless to an options seller. Third, whether it shows its math. If you cannot see which fee lines produced the total, you cannot verify it. Unverifiable math is just a number with confidence.
The biggest value is comparative, not absolute. Roughly $400 a year at Broker A versus roughly $150 at Broker B is actionable, even if both numbers are estimates. Precision matters less than the gap.
Run the audit once a year. Brokers adjust schedules, your habits change, and last year's cheapest broker is not always this year's. Pair it with a broker fee alert app with push notifications so you hear about changes between audits. Treat the whole thing as a brokerage fee comparison with your own data plugged in, which is the only comparison that ever mattered.
Want a second pair of eyes on the audit? BrokerCompare's onboarding calls walk through your fee math line by line. Start at brokercompare.fyi.