The Inverted V is 4% shorter than the Dipole. Which will be closer to 50 ohms between 35-45 degrees. When installing the wire, always cut longer then trim to the obtain the best SWR. Because of surroundings, the best results will normally require slightly different lengths than shown by the calculator.
If using insulated wire, do not worry at all about having to adjust the calculations. The velocity factor is usually around 99%, and since we always need to adjust for the surrounding, it will not cause any major changes to the calculations.