approximating the expected lives of the awards during the period, which approximate the rate in effect at the time of the grant.
On December 1, 2020, employees were granted the right to purchase an aggregate of 74,752 shares under the ESPP, and compensation expense related to those purchase rights for the three and nine months ended March 31, 2021 was $87,000 and $185,000, respectively. Employees purchased an aggregate of 57,361 shares under the ESPP for the nine months ended March 31, 2021.
On December 1, 2021, employees were granted the right to purchase an aggregate of 86,928 shares under the ESPP, and compensation expense related to those purchase rights for the three and nine months ended March 31, 2022 was $138,000 and $185,000, respectively. Employees purchased an aggregate of 64,666 shares under the ESPP for nine months ended March 31, 2022.
On December 17, 2021, our board of directors authorized an additional 600,000 shares of common stock to be available for issuance under ESPP. As of March 31, 2022, there were 1,178,409 shares of common stock available for issuance under the ESPP.
We base our estimate of expected life of a stock option on the historical exercise behavior and cancellations of all past option grants made by the Company during the time period which its equity shares have been publicly traded, the contractual term of the option, the vesting period and the expected remaining term of the outstanding options.
In accordance with ASU 2016-09, Compensation—Stock Compensation: Improvements to Employee Share-Based Accounting, we elected to continue to estimate forfeitures in the calculation of stock-based compensation expense.
As of March 31, 2022 there was approximately $13.6 million of total unrecognized compensation cost, net of expected forfeitures, related to unvested stock options, which is expected to be recognized over the weighted-average period of 1.8 years. There were 327,738 and 43,796 options exercised during the three months ended March 31, 2022 and 2021, respectively. There were 525,217 and 213,850 options exercised during the nine months ended March 31, 2022 and 2021, respectively.
Leases
Lease agreements are evaluated to determine whether an arrangement is or contains a lease in accordance with ASC 842, Leases.
Operating leases are included in operating lease right-of-use (ROU) assets, current operating lease liabilities, and noncurrent operating lease liabilities in the condensed consolidated financial statements. ROU assets represent the Company’s right to use leased assets over the agreed upon term. Lease liabilities represent the Company’s contractual obligation to make lease payments over the lease term.
For operating leases, ROU assets and lease liabilities are recognized at the commencement date of the lease. The lease liability is measured as the present value of the lease payments over the lease term, using the rate implicit in the lease if readily determinable. If the rate implicit in the lease cannot be readily determined, the Company uses its incremental borrowing rate at lease commencement. The operating lease right-of-use assets are calculated as the present value of the remaining lease payments plus unamortized initial direct costs and any prepayments, less unamortized lease incentives received.
Operating leases typically include non-lease components such as common-area maintenance costs. We have elected to include non-lease components with lease payments for the purpose of calculating lease right-of-use assets and liabilities, to the extent that they are fixed. Non-lease component payments that are not fixed are expensed as incurred as variable lease payments.
Lease terms may include renewal or extension options to the extent they are reasonably certain to be exercised. The assessment of whether renewal or extension options are reasonably certain to be exercised is made at lease commencement.