Mothers tend to be more generous, the research suggests. They expect to spend around £117 on a present, while fathers averaged gifts of around £94 in value.
Contributing to prom costs was the most popular reward on offer generally, with nearly one in three (30%) parents saying they had offered to do this.
Nearly one in four (22%) were offering their children hard cash as a reward, while about one in six (15%) was planning to pay for a meal out to toast their offspring's success.
Some parents promised big ticket purchases to motivate their teenagers. One in 11 (9%) said they would contribute towards a car, while 13% planned to help fund a holiday.
The survey of 1,000 parents by VoucherCodes.co.uk found that those in the East Midlands gave the largest cash rewards on results day, at £131 typically.
Students in East Anglia stand the best chance of being rewarded with a holiday, with their parents spending £217 on average on a trip away, the findings suggest.
Parents in Scotland were least likely to reward their children for good grades, with 26% saying they will not be offering rewards.
Of the motivational gifts parents have promised across the survey, the average expected cost will be:
- £136 towards a holiday
- £125 towards a laptop or computer
- £107 towards a tablet
- £105 towards a car
- £98 on a new mobile phone
- £98 in financial rewards
- £95 towards a games console
- £68 for a meal