Gartner’s $4.05T AI forecast and Forrester’s Predictions 2027 put the AI spending slowdown in 2028

Gartner and Forrester both forecast AI spending rising in 2027. Gartner’s October 7 AI spending forecast puts worldwide AI spending at $4.05 trillion next year, up 47% from $2.75 trillion in 2026, while Forrester’s Predictions 2027, published October 21, says one dollar in five of business technology spending will go to AI.
Each firm places the slowdown somewhere specific. In Gartner’s model, 2027 adds $1.30 trillion in new AI spending, the most of any year through 2030, and growth then drops to 28% in 2028 and 15% by 2030. Forrester’s pressure lands on budgets instead. Only 53% of tech leaders expect their budgets to beat inflation, so leaders plan their deepest cuts in services.
I built this comparison from Gartner’s 3Q26 AI spending forecast (G00862061) and the workbook Gartner publishes with it, Gartner’s October 21 IT spending forecast and Forrester’s public Predictions 2027 materials. The subtractions, shares and dollars added are my calculations.
Four numbers that frame Gartner and Forrester AI spending in 2027
- Gartner added $413 billion to its 2027 AI forecast in one quarter. AI infrastructure rose $420 billion from the July forecast, more than the total increase, because Gartner trimmed AI software by $8 billion.
- 2027 is the peak year for new AI dollars in Gartner’s model. Spending adds $1.30 trillion in 2027, then $1.14 trillion in 2028, $920 billion in 2029 and $897 billion in 2030.
- The two headline numbers measure different things. Gartner sizes the whole AI value chain, chips and consumer devices included. In contrast, Forrester sizes AI’s share of business technology spending.
- Both firms see services absorbing the squeeze. Gartner forecasts IT services growing 4.9% in 2027 while data center systems grow 55.5%. Meanwhile, Forrester says leaders already plan their deepest cuts in services.
















