Cost of capital explained: this guide covers what it means, who it applies to, the step-by-step process, documents required, fees, due dates and penalties in India — so you can stay compliant with confidence and avoid costly mistakes.
Every rupee a business uses has a price, whether it is interest on a loan or the return owners expect on their money. A new project that earns less than the blended price of the funds behind it makes the owners poorer. The weighted average cost of capital (WACC) is that blended price, and finance managers and owners of private companies use it as the hurdle for investments.
Cost of capital is the minimum return a project must earn to satisfy those who funded it. Compute each source's cost on an after-tax basis, weight it by its share in the funding, and add: WACC = sum of (weight x cost). Use it as the discount rate or hurdle for projects of average risk, and reject, or at least question, any project that is expected to earn less than WACC.
When to use it and what data you need
Owners who lack an in-house finance head often take this work to a virtual CFO. Use it before approving a new machine, product line or branch, when comparing financing plans, and when setting a target return for managers. You need the loan terms (rate, fees), the preference terms if any, the dividend and growth expectation or a return the owners ask for, the tax rate, and the amounts of each source. Our guide on sources of finance lists what is available to a firm.
The cost of each source
| Source | Formula in words | Symbols |
|---|---|---|
| Debt (after tax) | Interest rate times one minus the tax rate | Kd = i x (1 - t) |
| Preference capital | Preference dividend over net proceeds | Kp = D / P |
| Equity, dividend growth approach | Next year's dividend over price, plus growth | Ke = D1 / P0 + g |
| Equity, risk premium approach | Baseline rate on government securities plus beta times the market premium | Ke = Rf + b x (Rm - Rf) |
| New equity with issue cost | Next dividend over price net of issue cost, plus growth | Ke = D1 / + g |
| Retained earnings | Same as the cost of existing equity | Kr = Ke |
Debt is cheaper because interest reduces tax; for the tax effect, see our income-tax guides. Equity costs more because owners carry the risk of being paid last. Retained earnings are not costless: the owners could have taken the profit and invested it elsewhere, so they expect the same return as on equity, with no issue cost.
Weights. Book-value weights use the amounts in the balance sheet and are simple. Market-value weights use the current value of each source and reflect today's reality, but need a value for equity, which a private company must estimate. Target weights use the mix the firm plans to hold. Whichever you use, apply it consistently and say so.
Marginal cost of capital. The cost of the next rupee raised can differ from the average, for example when cheap debt runs out and new equity with issue cost must be used. Use the marginal figure for a project that needs a fresh round of funding.
Worked example: Sunrise Plastics Private Limited
Sunrise Plastics is an invented company. All rates are assumed for illustration: tax 25 per cent; baseline rate on government securities 7 per cent; market premium 7.5 per cent; beta 1.2.
Capital (₹ lakh, book values): term loan 40 at 12 per cent interest; preference capital 10 at 10 per cent dividend, issued at par; equity share capital 20; reserves 30. Total 100. The shares carry an agreed value of ₹80 each; next year's dividend is expected at ₹8 per share, growing at 6 per cent a year.
Step 1: costs
- Debt: 12 x (1 - 0.25) = 9.00 per cent.
- Preference: 10 / 100 = 10.00 per cent.
- Equity, dividend growth: 8 / 80 + 0.06 = 0.10 + 0.06 = 16.00 per cent.
- Equity, risk premium: 7 + 1.2 x 7.5 = 7 + 9 = 16.00 per cent.
- Retained earnings: 16.00 per cent, the same as equity.
- For comparison, new equity with a 5 per cent issue cost: 8 / (80 x 0.95) + 0.06 = 8 / 76 + 0.06 = 10.53 + 6 = 16.53 per cent.
The two approaches agree here by construction; in practice they differ and the owners should judge between them.
Step 2: book-value WACC
| Source | Amount | Weight | Cost | Weight x cost |
|---|---|---|---|---|
| Term loan | 40 | 0.40 | 9.00% | 3.60% |
| Preference capital | 10 | 0.10 | 10.00% | 1.00% |
| Equity and reserves | 50 | 0.50 | 16.00% | 8.00% |
| Total | 100 | 1.00 | 12.60% |
Step 3: market-value weights. Suppose the owners value equity and reserves together at ₹90 lakh while loan and preference stay at their book amounts. Total = 40 + 10 + 90 = 140. Weights: 40/140 = 0.2857, 10/140 = 0.0714, 90/140 = 0.6429. WACC = 0.2857 x 9 + 0.0714 x 10 + 0.6429 x 16 = 2.571 + 0.714 + 10.286 = 13.57 per cent.
Decision. Rounded to two decimals, WACC is 12.60 per cent on book weights and 13.57 per cent on market weights. Sunrise's owner sets 13.57 per cent as the hurdle for new projects of similar risk: a machine expected to return 15 per cent passes, one returning 12 per cent does not. If the machine will be funded wholly by a new loan, the owner should also look at the marginal cost, as debt capacity is limited; the capital structure effect is covered in EBIT-EPS analysis.
How to read the result
WACC is a hurdle for a project that has the same risk as the business. A riskier project deserves a higher hurdle, as explained in risk in capital budgeting. Cost of capital also guides the choice of mix: more debt lowers the average until the added risk raises the cost of equity and the lenders' rate.
Common mistakes
- Using the before-tax interest rate instead of the after-tax cost.
- Treating retained earnings as costless.
- Using the coupon or the stated dividend rate of old preference capital when current terms differ, or the book return on equity in place of the return owners expect.
- Mixing book weights for some sources and market weights for others.
- Applying one WACC to every project regardless of risk.
- Forgetting issue costs when new capital will be raised.
- Using a growth rate higher than the economy can sustain.
Where the company lends or invests in other companies, company law limits apply; see section 186. The result is only as good as the inputs, and the growth rate and the return owners expect are judgments.
Need help with cost of capital?
If you want a finance partner to set the hurdle rate and test projects against it, our virtual CFO services include capital structure and investment reviews. We work from your own loan papers and accounts and agree the assumptions with you before the numbers are used.
Key takeaways
- Cost of capital is the minimum return that satisfies the funders of a project.
- Debt is measured after tax; equity by dividend growth or by a baseline rate plus risk premium; retained earnings cost the same as equity.
- WACC is the sum of weight x cost; state whether weights are book, market or target.
- Use WACC for projects of average risk; adjust upward for riskier ones.
- Use the marginal cost when a project needs new funds.
Read next
- Capital structure decisions: EBIT-EPS analysis
- Capital budgeting: payback, NPV, IRR
- Sources of finance for a business
Disclaimer: The methods described are standard cost accounting and financial management techniques. The worked example uses an invented business and invented figures, including any tax, interest or exchange rate, which are assumptions for illustration and not current rates. Where the article refers to a legal requirement, the linked guide and the official text should be checked. This article is general information, not legal advice; check the official text before acting.