Fears of escalating the conflict mean that NATO members including Britain are limited in what military hardware they can send to Ukraine.
The minister said that Britain's assessment was that "approximately 15,000 Russian personnel have been killed during their offensive (and) over 2,000 armoured vehicles have been destroyed or captured".
Over a quarter of the more than 120 battalion tactical groups Russia had committed to invading Ukraine "have been rendered not combat effective", Wallace said.
He said Britain's military contribution so far included 5,000 anti-tank missiles, five air defence systems with over 100 missiles and 4.5 tonnes of plastic explosive.
Prime Minister Boris Johnson recently said Britain would send 120 armoured vehicles to Ukraine, as well as anti-ship missiles. US Defence Secretary Lloyd Austin said on Monday that Ukraine can win the war against Russia if it has the "right equipment".
The bloody conflict has triggered an outpouring of support from Western nations that has seen a deluge of weapons sent to Ukraine to help beat back the Russian invaders.