How about this?
According to it:
A 10% change in airspeed will cause a 20% change in in stopping distance.
For each knot of airspeed above Vref over the numbers, the touchdown point will be 100 feet further down the runway.
A 1,000' change in field elevation will cause a 4% change in stopping distance (higher airfield, longer stopping).
A 10deg C deviation from standard temperature will cause a 5% change in stopping distance (higher temp, longer stopping).