According to the 10 per cent law of energy flow in ecosystems, only 10 per cent of the energy is transferred to each trophic level from the lower trophic level . Since energy flows unidirectionally and decreases at successive levels , the energy at lower levels is calculated by dividing the higher level's energy by 10% (0.1). Calculation:

• T4 = 1000 J
• T3 = 1000 J / 0.1 = 10,000 J
• T2 = 10,000 J / 0.1 = 100,000 J
• T1 = 100,000 J / 0.1 = 1,000,000 J