Normalizing cross-correlation to [-1,1] for different length signals

Hello

I have the following piece of code for calculating the cross-correlation between to signals. Visually, the signals are correlating very well. The signals are of different length but both have a sampling rate of 100Hz. There is a lag between the signals (called timeDiff below).

[acor,lag] = xcorr(signal1,signal2);
[cor,I] = max(abs(acor));
lagDiff = lag(I);
timeDiff = lagDiff/100;
fprintf('Correlation = %0.5f \n',cor);

I'm getting a correlation of 6239.06131. How can I normalize this to -1 and 1? Because otherwise it is hard to interpret.