# How long until TagTime's estimate is accurate?

It looks like you need about 200 hours’ worth of pings (5 weeks of full-time work) before you can be 90% sure that TagTime’s estimate has less than a 10% error. But the estimate will be probably approximately correct much sooner than that. For example, you can be essentially completely certain that TagTime’s estimate is within a factor of 2 of ground truth by the time TagTime reports 20 hours.

And if you just need it to be right to within an order of magnitude you can be pretty sure of that by your 2nd ping.

That’s assuming the standard 45-minute average gap between pings.

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To clarify how to use Tminder to figure such things out:

You can ask it, if you need 200 hours, what’s the probability of that many (267) pings happening in less than 180 hours (answer: less than 5%) and then ask what’s the probability of 267 pings taking more than 220 hours (answer: almost 6%). So that means it’s about 90% that 200 hours worth of pings will happen in 180 to 220 hours.

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