Brief overview: 1/5
2/5 Ukraine had 858 tanks at the beginning of the war (the Military Balance). In 14 months, 605+ tanks were delivered by the Allies (including about 90+ Leopard 2 and Challenger 2 tanks). Another 80 Leopard 1 will arrive in June. Also, the AFU captured at least 544 Ru tanks
3/5 Oryx estimates UA losses at 495 tanks. According to experts, Oryx data cover about 80% of total losses. Therefore, the total losses of UA may amount to 620 tanks.
Thus, the available number of tanks for a counteroffensive is 1400 or so.
4/5 Russia had 3330 (the Military Balance). In 14 months, Roux was able to produce or know from storage 600+ tanks.
Oryx estimates RU losses at 1,911 tanks. Therefore, total losses can amount to 2,400 tanks. Thus the available number of Roo tanks is 1500 or so.
5/5 At the same time, Ru attracted rather old T-62 and T-55 tanks. During the war, the Allies supplied UA with 5,500+ armor. This is double what the UA had at the beginning of the invasion. Therefore, Ukraine now has much more resources than in the autumn of last year.