The leverage is the amount of debt in a company.
When you decide to assess the leverage capacity of a company, you want to know the maximum leverage of the company.
When you want to assess a maximum leverage you need to make sure that the company can repay 1) interest expense and 2) the principal.
To do so, it is important to look at cash flow before debt service, its evolution and sensitivity to different parameters (sales growth, costs evolution etc…). This cash flow will have to be sufficient to 1) pay interest, 2) pay principal and 3) gives some headroom to allow the company to grow or face bad situations.
You can back-calculate the maximum leverage by taking the amount you can afford to give up to the debt holder.
To assess maximum leverage, you need to also look at the market: are companies in this sector very levered? Are banks landing money to this type of companies?
To assess leverage for a target, the financial sponsor need to be sure that the company can repay the debt quickly and gives space for equity value creation! If you have too much debt, equity value might get to 0 if things go badly!