RGU said a downturn in the regional economy due to the falling oil price had affected the university's income.
It also reported a reduction in demand for courses from students from oil-producing countries.
RGU said the aim was for the savings to be made through a voluntary redundancy scheme.
Prof Ferdinand von Prondzynski, principal of the university, said: "RGU will embark on a period of re-profiling its workforce to address the financial challenges and our strategic needs, allowing us to pursue ambitious targets for the successful, sustainable development of the university.
"We will continue to make a leading contribution to economic growth here and across Scotland, widening access to higher education, and the availability of high value knowledge and skills for the economy and society."
An additional £2m of savings are to be made via operational costs.

Mitzi Steady, four, Robert Parker, 59, Philip Allen, 52, and Stephen Vaughan, 34, died in the crash in February 2015.
Bristol Crown Court was told the truck was too big to legally travel down Lansdown Lane in Bath.
Driver Phillip Potter, 20, of Dauntsey, denies causing the deaths by dangerous and careless driving.
His boss Matthew Gordon, 30, of Dauntsey, who was driving another truck in front of Mr Potter, also denies 14 offences while the truck company's mechanic Peter Wood, 55, of Brinkworth, denies four charges.
Prosecutor, Adam Vaitilingam QC told the court Lansdown Lane, which has a 6ft (1.8m) width restriction for HGVs, was known locally as a "rat run".
He said: "These two lorries were both a lot wider that 6ft - they were about 8.5ft (2.6m) wide - and they were not using Lansdown Lane for access - they were using it as a short cut.
"They were ignoring the prohibitions. These lorries were not allowed to be and should never have been on Lansdown Lane."
The jury heard tachograph records show the drivers had not taken mandatory breaks in the hours before the collision and both lorries were speeding as they approached Lansdown Lane.
Mr Vaitilingam said the ABS warning light, which indicates problems with the braking system, was on in Mr Potter's lorry meaning it should not have been driven.
Mr Potter and Mr Gordon were driving two trucks carrying 32-tonne loads from a Wiltshire quarry on 9 February last year when the crash happened.
The court previously heard the brakes of Mr Potter's truck failed and the vehicle hit several pedestrians including Mitzi and a car containing Mr Allen and Mr Vaughan, both from Swansea, and Mr Parker, from Cwmbran, south Wales.
Mr Potter is also charged with causing serious injuries to Karla Brennan and Margaret Rogers - Mitzi's grandmother - by dangerous driving.
He denies a total of 10 charges against him.
The trial continues.
Aberdeen's Robert Gordon University (RGU) is to cut staff costs by £4m - meaning about 100 jobs are expected to be lost.
[NEXT_CONCEPT]
A 32-tonne tipper truck was too wide to be driven on the steep road where it crashed and killed four people, a court has heard.