Few companies grow in a straight line. A young dividend payer might raise its payout 15 percent a year for five years, then settle into a sedate 5 percent forever as it matures. Valuing that two-act story needs a two-stage model: discount each high-growth dividend individually, then value the stable phase with the Gordon formula and discount that terminal value back to today. The sum is the intrinsic price.

This calculator stages the whole production. Enter the current dividend, the high-growth rate and its duration, the stable growth rate, and your required return -- the defaults ($1.50, 15 percent for 5 years, then 5 percent, discounted at 10 percent) mirror a maturing growth stock. It shows dividends at years 1, 3, and 5, the terminal value at the end of the high-growth phase, the present value of the phase-one dividends, and the final intrinsic stock price.

The terminal value usually dominates the answer, which makes the stable-phase assumptions the ones to scrutinize. A single point of extra perpetual growth inflates the valuation enormously -- the model's famous sensitivity. Use the tool to test scenarios: what is the stock worth if high growth lasts three years instead of five, or if stable growth is 3 percent rather than 5? The range of answers is more truthful than any single number.

With the pre-filled defaults — Current Dividend (D0) $1.5, High-Growth Phase Rate 15%, High-Growth Phase Duration (Years) 5, Stable Growth Rate 5%, Required Rate of Return 10% — the Non-Constant Growth Stock Calculator returns Dividend Year 1 $1.7250, Dividend Year 3 $2.2813, Dividend at End of Phase 1 $3.0170, Terminal Value $63.36, PV of Phase 1 Dividends $8.59, Intrinsic Stock Price $47.93. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.