Business Valuation

What is free cash flow?
It is the cash that is free to be distributed to share holders of the company to keep investors happy.
Hence we calculate NOPAT (Net Operating Profit After Tax) and subtract Net CAPEX (Capital Expenditure) from the NOPAT. CAPEX is subtracted because it is the investment already made by the company to grow its revenue. hence it is not available to the share holders.Change in Net Working Capital is also subtracted from NOPAT since it seems that next year they might need that changed working capital in addition to the already deducted working capital from NOPAT.
FCF = NOPAT - Net CAPEX - Delta NWC

Calculate NOPAT
NOPAT is calculated easily (EBIT * (1 - Tax Rate)). However, it is the adjustments that need to be made on NOPAT that makes it complicated. Without adjustments, NOPAT value in itself is not sufficient to use in any kind of analysis.

Adjustments that go on NOPAT are any expenses that are one time expenses like restructuring charges or interest portion of operating lease payments since interest expense should not be deducted from NOPAT. Interest expense is not related to operations of the company so it is wise to add it back to Net Income/EBIT.

Calculate Net CAPEX

Capital Expenditure is money invested back into the company for future growth. Hence this money is not available to share holders. Hence it is deducted from the NOPAT to arrive at Free Cash flow.

The Capital Expenditure is mentioned in the Cash Flow Statement of company's financials.

Adjustments are made to Net CAPEX for depreciation. Depreciation is subtracted from capital expenditure All the investing activities which bring in money like sale of assets are subtracted from the CAPEX. All investing activities that result in outflow of cash are added to CAPEX like acquisitions.

Calculate Change in Net Working Capital (NWC)

Net Working Capital can be calculated as

Accounts Receivables + Inventory - Accounts Payable

Free Cash Flow (FCF)

FCF = NOPAT - CAPEX - change in NWC

Equity Valuation

To come to the Equity value of the company, you have to estimate the revenue for the next 5 years, estimate NOPAT as a % of Revenue, estimate CAPEX as % of Revenue, estimate change in NWC and calculate FCF for next 5 years. For years thereafter, assume a growth rate generally assumed to be 3%, and calculate Terminal Value. Calculate present Value for all the FCF values and sum them up to get the Equity Value of the Enterprise.

Debt Value

Debt value can be calculated by calculating present value for all future debt obligations and summing them up.

Enterprise Value

Enterprise Value is the sum of Debt Value and Equity Value.