DFT Signal DFT Length N , FFT
For a time domain signal the length or the number of samples in the sampled signal can be computed as shown in Equation $(1)$
$$
T = NT_s \equiv T = \frac NF_s \implies N = TF_s\tag{1}
$$
Where $T$ is the signal total duration in [seconds] and $F_s$ is the sampling frequency in [Hertz], and $N$ the total number of samples.
The length of the DFT depends on the number of point taken in computing the DFT. For a $N$-point DFT on a signal of $N$ total samples you have $N$ as the length of your DFT.