It depends on a few factors. I would say that it's the investors that value your company, not you. Until there's a (first) funding event, valuation is a theoretical thing.
A bit like real estate, your home is worth what the offer comes at.
That said, it depends on the potential of the idea, the size of the market, how far you're into the product development, the team you have assembled, and what the investor thinks it's worth. If all else fails, pick a number between $1-7 million.
Your valuation is whatever someone is willing to pay you for your company. Instagram was bought for ~$1Bn, therefore, it was worth ~$1Bn, whatever anyone else says.
As others have said, your investors define your valuation, and anyone looking to acquire you, even more so. A lot of companies look at revenue, users, and technology IP, but with more companies starved for talent, you should also take your human capital into consideration. An acqui-hire ain't always a bad way to go.
I have invested in 2 pre-launch companies in the past 6 months and evaluated more than 100 companies raising funds pre-launch in the past 3 months.
In today's world, the minimum bar you should set is a $1,000,000 pre-money valuation. The reason being is that if you accept money for less than that, given today's surplus of early-stage funding, it's a negative signal to future investors.
Today's ceiling for a sophisticated investor valuing a pre-launch startup is $5m and that's with exceptional founders or great founding teams.
So now you have a range by which to navigate within. Further context that will be helpful to you is for you to determine how much you really need to raise to demonstrate traction. It will be much harder for you to raise further funding if you have launched but failed to get substantial validation from your users. So you want to ensure that you can execute the plan you think will work, and ideally have additional funding for some contingency plans. In total, you should never give up more than 1/3 of the company in a pre Series A funding round. Doing so will mess up your cap table later on, and significantly reduce incentives for you and your team. So then, you get a much easier calculation.
Generally, good investors are fairly insensitive to a valuation under $3m.
Happy to talk to you about your funding plans.