In Dragon's Den, giving away one-quarter of a business means offering 25% equity.
Equity is the ownership portion of a company. When an entrepreneur offers 25% in the den, they are proposing that an investor receive one quarter of the business in exchange for money, expertise or both. The percentage is separate from the cash valuation implied by the pitch.
For example, an offer of £50,000 for 25% implies a post-money valuation of £200,000, assuming the entire proposed deal is accepted. The calculation is £50,000 divided by 0.25. Actual agreements may later change during due diligence, so a television offer is not automatically a completed investment.
Viewers sometimes confuse equity with profit share or a loan. Equity represents ownership, while a loan normally has to be repaid and does not itself transfer company ownership. Dragon's Den pitches use percentages because entrepreneurs negotiate ownership directly with the investors.