True-Type_Font Monospace


I rendered a Text with Bitstream-Vera-Sans-Mono.ttf
I thought a monospaced font has equidistant width.
This is what the output says about the width:

letter_rect[3].w = e = 47
letter_rect[4].w =w = 49
letter_rect[5].w = r = 48

and this is the code to generate the width:

letter[1] = ‘\0’;
for (i=0; i < stringlength; i++) {
letter[0] = string[i];

	letter_surf[i] = TTF_RenderText_Solid(font, letter, white);
	letter_rect[i].w = letter_surf[i]->w;
	letter_rect[i].h = letter_surf[i]->h;


What can I do to get equidistant widh?

Thanks for your help.