Ask HN:About Software Estimation

Is software estimation relevant in this community? Assuming most of the folks here are working in startup environment, I am curious if software estimation is done and if yes how. I work in a big organization where estimation is done by a gut feeling of someone senior and often outdated with latest technology trends. This result in over estimation of as much as 5 times (sometimes 10 times) the actual effort required. I wonder if software estimation is an art or science. Please point out to some good resources to learn good software estimation.