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Open rate, click rate, click-to-open, conversion rate and email ROI - one calculator for all five, with the formulas shown so the math is never a mystery.
Email platforms show you a wall of metrics. Five of them carry most of the meaning, and each answers a different question about the same send.
Open rate is unique opens divided by delivered emails. It mostly measures your subject line, your sender name, and whether people still trust you enough to look. One honest caveat: Apple Mail pre-loads opens for privacy, so reported open rates have run high since 2021. Watch your trend, not the absolute number - a steady drop means something changed, even if the number itself is inflated.
Click rate (clicks divided by delivered) measures the whole send. Click-to-open rate (clicks divided by opens) isolates the content: of the people who opened, how many found a reason to click? If open rate is healthy but CTOR is weak, the subject line promised something the email did not deliver. If both are weak, the problem starts earlier.
Conversion rate is the share of delivered emails that produced the action you wanted - a purchase, a signup, a reply. ROI puts a price on it: revenue minus cost, divided by cost. Be honest in the cost line: platform fees plus the hours you spent, priced at something. An email that "made" $200 on ten hours of work did not make $200.
Read the five as a funnel: delivered → opened → clicked → converted → profitable. The worst stage is the one to fix first. A brilliant call to action cannot rescue an email nobody opens, and a great subject line cannot rescue an offer nobody wants.
Open rate = unique opens divided by delivered emails, times 100. Delivered means sent minus bounces. A 1,000-email send with 20 bounces and 420 opens has an open rate of 420 / 980 = 42.9%.
Click rate (CTR) divides unique clicks by delivered emails and measures how the whole send performed. Click-to-open rate (CTOR) divides unique clicks by unique opens and measures how well the email's content worked on the people who opened it.
Small, engaged lists often see 35 to 50 percent; large, mixed lists typically land lower. Treat any benchmark as rough context only - your trend over time matters more than any industry number, and Apple Mail privacy opens inflate all reported open rates.
Email ROI = (revenue attributed to the email minus total cost) divided by total cost, times 100. Include your platform cost and the value of your time in the cost, or the number flatters you.