Stop guessing which campaigns work
Marketing runs on numbers that look precise and aren't. A test shows a 12 percent lift after three days. Is that real? A channel reports a $38 cost per lead. Is that good? The answer depends on what a lead is worth to you.
The eight tools here help you answer those questions with arithmetic. They run in your browser, and your data stays on your device.
Testing: sample size and significance
Run an A/B test without enough visitors and you'll declare winners that aren't. The sample size calculator tells you how many visitors each variation needs before you start. You set a baseline conversion rate, the smallest lift you care about, significance and power. It also estimates how many days the test will take.
The significance calculator works on finished results. Enter visitors and conversions for both versions and it runs a two-proportion z-test and returns a p-value. A low p-value suggests the difference isn't just noise.
Don't peek and stop early. Checking daily and ending the test when it looks good inflates false positives. Decide the sample size up front and wait.
Ads: break-even CPC and cost per lead
The Google Ads CPC break-even calculator finds the most you can pay per click without losing money. It works from margin and conversion rate, for either e-commerce or lead generation, and can add a ROAS cap. Bid above that number and every click costs you.
The LinkedIn Ads CPL calculator suits B2B. It starts from deal value and close rate to find the cost per lead you can afford, then walks the funnel from budget to leads. Green and red indicators show headroom. LinkedIn leads cost more than most channels, but one closed deal can pay for hundreds of them.
Both tools make the same point. You can only judge an ad price once you know what a customer is worth.
Email, links and conversion
The email ROI calculator follows your list through to revenue: list size, open rate, click rate, conversion and order value. It compares your return with the often-quoted 36 to 1 benchmark. Treat that benchmark as a ceiling. Many lists earn far less.
The UTM link builder creates tagged URLs with source, medium and campaign values, previews the result and maps it to GA4 channels. It can build up to twenty links at once. Pick naming rules and stick to them. "Facebook", "facebook" and "fb" show up as three separate sources.
The conversion rate lift calculator compares four scenarios and shows what each one adds in monthly and yearly revenue and profit. A one point lift on a busy store is worth real money.
Creator revenue
The YouTube AdSense estimator uses RPM bands by niche, adds Premium uplift, memberships and Super Chat, and projects 0, 10 and 20 percent monthly view growth. It's a planning aid. Real payouts swing from month to month.
Common errors to avoid
Testing too many changes at once. If you change the headline, image and button together, you won't know which one moved the number.
Ignoring seasonality. A test run during a holiday week tells you about the holiday.
Tracking clicks instead of customers. A cheap click that never buys is expensive.
Letting UTM tags drift. Messy tags make reports useless, and you can't fix history later.
A simple order of operations
First work out what a customer is worth. Then set your maximum cost per lead and per click. Build tagged links. Run tests with a sample size you've calculated, not guessed. Review results with the significance tool.