Return on investment is one of those numbers everyone quotes and few calculate the same way twice. This post covers the actual formula, a couple of worked examples using real business scenarios, and the specific situation where a plain ROI number will mislead you. If you just need the number quickly, our free ROI calculator does the math for you, this post explains what it is doing and why.
The basic ROI formula
ROI is expressed as a percentage:
ROI = (Net Profit from Investment / Cost of Investment) x 100
Where Net Profit from Investment is what you got back minus what you put in.
A worked example: you spend ₹50,000 on a Google Ads campaign for your shop over three months. Sales you can directly attribute to that campaign come to ₹80,000 in gross revenue. If your product margin is 40%, your gross profit from those sales is ₹32,000. Your net profit from the investment is ₹32,000 minus the ₹50,000 you spent, which is a loss of ₹18,000.
ROI = (-18,000 / 50,000) x 100 = -36%
That campaign lost money on a pure ROI basis, even though it generated ₹80,000 in sales, because the cost of acquiring those sales was higher than the profit margin on the products sold. This is the single most common mistake small business owners make when judging ad spend: looking at revenue generated instead of profit generated.
A second example, this time profitable
You spend ₹15,000 building a website with a domain and basic SEO setup. Over the following year, you can trace ₹120,000 in sales directly to enquiries that came through the website (WhatsApp clicks, contact form, or a tracked phone number). At a 35% margin, that is ₹42,000 in gross profit.
ROI = ((42,000 - 15,000) / 15,000) x 100 = 180%
A 180% ROI means you made ₹1.80 in profit for every ₹1 spent, on top of getting your original investment back. This is a genuinely strong number, and it is the kind of return a website or domain purchase can realistically produce over a year when it is actually driving enquiries, which is why we built this alongside tools like the website cost breakdown guide, most owners underestimate the return relative to the cost.
Where simple ROI misleads you
Simple ROI does not account for time. A 180% return over one year and a 180% return over five years are very different outcomes, but the plain formula treats them identically. This matters most when comparing two investments with different timeframes.
If Investment A returns 50% over 6 months and Investment B returns 80% over 2 years, plain ROI makes B look better. But annualized, A is compounding much faster. The annualized ROI formula adjusts for this:
Annualized ROI = ((1 + ROI)^(1/n) - 1) x 100, where n is the number of years
For Investment A (50% over 0.5 years): ((1.5)^(1/0.5) - 1) x 100 = 125% annualized
For Investment B (80% over 2 years): ((1.8)^(1/2) - 1) x 100 = 34.2% annualized
Once you annualize, A is clearly the faster-compounding investment, even though its raw ROI number looked smaller. Use annualized ROI whenever you are comparing options with different time horizons, which covers most real business decisions: comparing a one-time marketing push against a subscription tool, or comparing this year's equipment purchase against last year's.
What counts as "cost of investment"
Getting the cost side right matters as much as the profit side. For a fair ROI calculation, include:
- The direct spend (ad budget, tool subscription, equipment price)
- Setup or one-time costs (design, delivery, installation)
- Your time, valued at what you would otherwise be paid or what it would cost to hire out, if the investment consumed significant hours
Leaving out your own time is the most common way small business owners overstate ROI on things like building their own website or running their own marketing, the tool might be free or cheap, but if it took 40 hours away from running the business, that has a real cost.
What counts as "return"
Only count profit that is genuinely attributable to the investment, not total revenue during the period. This requires some form of tracking, a dedicated phone number, a discount code, a "how did you hear about us" question, or UTM-tagged links using something like our UTM builder, so you can separate sales the investment caused from sales that would have happened anyway.
Quick reference
- Simple ROI: (Net Profit / Cost) x 100, use for single-period comparisons
- Annualized ROI: use when comparing investments with different time horizons
- Break-even point: if you want to know not just the return but how long until you recover the initial cost, our break-even calculator handles that calculation
- Margin matters: always convert revenue to profit using your actual margin before calculating ROI, our profit margin calculator does this step
For a business owner deciding where to spend the next ₹10,000, whether that is ads, a website upgrade, or new equipment, running the actual numbers through this formula takes five minutes and regularly changes the decision.