How accurate is income driven repayment calculator on Nelnet website?

I have approximately $196,000 in student loan debt, with a gross income of $120,000. When I use the income-driven repayment calculator on Nelnet’s website, it estimates my repayment could be $275 on an income-driven repayment plan. However, when I use the government site’s calculator, it estimates payments starting at $840 per month, increasing to $1,300 per month. Which estimate is more accurate? Why is there such a difference between the two?

Payments are based on AGI not gross income. The formula is very straightforward. Just calculate on your own. If it’s asking for gross, they might just be assuming age.