What are the methods and guidelines for calculating the number of program hours per project?

Question

Project management

Hello.
I'm quite new to calculating the number of hours needed to complete a project.
And this property of the project is often used when calculating its final cost.
When they ask me: - How many hours will it take? - I usually just shrug my shoulders: - How the stars will line up... how often will you make adjustments... how competent is the layout of your template, which "needs to be pulled on the engine"... how timely and structured you will provide the data necessary for implementation ...
In general, in the end, the client often goes to where he is given specific numbers, although they almost always deceive (judging by the facts).
Are there any standards in this area?
What is the correct way to count these hours?
I see, I can’t even formulate the question properly :)
Just don’t advise me, please, to read some thick book with a lot of water.
I need some specific technology how to determine the number of project hours and not philosophy.
Thank you.

Answer 1

Bobuk method

Часто спрашивают, решил один раз написать. Срок выполнения любого проекта по Бобуку-Бацеку, формула от 2008 года

https://twitter.com/bobuk/status/636252417089212416
Specific technology
- take a piece of paper
- write down each task, what you are doing

What is a task

ето такой блок действий, который сложно разделить на подзадачи
Вначале нужно руководствоваться именно таким подходом
Когда у вас появятся групки задач, оценивайте их вместе

- under each task, write the number of hours that you intend to spend on the task
- at the initial stage, you can bet from the bulldozer
- after solving the task - write down the number from the tracker
- write a brief description of why the time does not match the calculated one
Repeat indefinitely

Answer 2

There are market rates for typical work, there are market rates for a freelancer's hour of work, there are features of the implementation technology that affect the cost. From here, based on the design of the system, you can calculate the total cost. The general recommendation is to multiply the result by a coefficient (everyone takes an average of 1.5 ... 2 in different ways).
ps topics with changes in requirements and lack of input data is a separate song.