### Author Topic: Math help - calculating time to crossover point  (Read 504 times)

#### RyanAtTanagra

• Handlebar Stache
• Posts: 1185
• Location: SF Bay, CA
##### Math help - calculating time to crossover point
« on: September 13, 2019, 03:07:40 PM »
I'm trying to figure out the math for calculating when I'm going to hit my crossover point (passive income equals expenses).  I want to incorporate current invested assets (and the return on them), as well as savings rate.

For an example of easy figures to work with:

500k invested assets
assume 7% return
annual savings of 50k
current expenses 40k (1 million needed)

Anyone know the math to calculate how many years to hit it?  I believe there's a natural log in there for the compounded return, but the specifics are beyond me.

#### terran

• Magnum Stache
• Posts: 3133
##### Re: Math help - calculating time to crossover point
« Reply #1 on: September 13, 2019, 04:20:43 PM »
In Excel =NPER(7%,50000,500000,-1000000) says 5.096 years.

#### RyanAtTanagra

• Handlebar Stache
• Posts: 1185
• Location: SF Bay, CA
##### Re: Math help - calculating time to crossover point
« Reply #2 on: September 13, 2019, 04:28:11 PM »
In Excel =NPER(7%,50000,500000,-1000000) says 5.096 years.

Yes, perfect!  Thank you!

#### terran

• Magnum Stache
• Posts: 3133
##### Re: Math help - calculating time to crossover point
« Reply #3 on: September 13, 2019, 04:53:45 PM »
In Excel =NPER(7%,50000,500000,-1000000) says 5.096 years.

Yes, perfect!  Thank you!

You're welcome!

I was a little worried it was a trick question and you wanted a "real math" answer. Glad this works for you.