Getting an Iran visa in advance is the safest way to avoid any kind of inconvenience, which could disturb your stay in Iran.

The duration of the visa is 30 days.

 This option is heavily recommended for tourists who would like to stay in the country for a stay to one month, or for those who don't want to take the risk of doing the Visa on Arrival (at the airport).

 It's also the only option you have if you want to go to Iran via a border crossing.

Process is relatively simple, you will have to go through 2 main steps, which is explained below: 

1. You will have to obtain an Iran visa Authorization Number , from the Iranian Ministry of Foreign Affairs (MFA) through an official Tour Operator in Iran(Nadiatrip)
2. Once you got this important Notice of Iran Visa, you must go to the embassy/consulate previously chosen to get your Standard Iran Visa. 

The only option you have to get this code is to contact Nadiatrip .

You will have to fill out a form about your personal details and your planned itinerary.

Nadiatrip tour operator will contact the Iranian Ministry of Foreign Affairs (MFA) on your behalf to request an Authorization Number of Standard Iran Visa.

The average time for getting the Grant Notice of Iran Visa is around 5 working days.

Be careful, in this form you will have to specify in which embassy/consulate you would like to pick up your Iran Visa.

As an Iranian Tour Operator, we are offering Iran Visa Grant Notice for the bargain price of 20 euros.

In general, we estimate that it should take around 5 working days for your Grant Notice of Iran Visa to be issued. 
Keep in mind that on Thursday, Friday and Saturday the Ministry of Foreign Affairs (MFA) is closed, and your Authorization Number of Iran Visa could be delayed because of various public holidays of the Iranian calendar.
We will send you an email once your Authorization Number of Iran Visa (Iran Visa Grant Notice) has been issued.

Once you receive an email from our agency with your Authorization Number of Standard Iran Visa, you can go to the embassy/consulate that you had previously chosen and start the second step of Iran Visa process. The documents you will have to bring differ from an embassy to another, and you should contact them before to make sure about what you really have to bring. Most of the embassies will require some identity photos (women do not need wear a scarf on the picture), a photocopy of your passport identity page, an attestation of insurance for the time you will be in Iran and enough money to pay for your Iran Visa embassy fee.

You will also have to fill another form with personal information at the embassy.
If your Iran Visa application is accepted, the embassy/consulate can issue your Standard Iran Visa in a few hours or in one or two weeks, depending on the location and the workload of the embassy/consulate. An emergency option is often offered by embassies and consulates in order to make your Iran Visa process faster if you are in a rush.

To obtain your Authorization Number of Iran Visa through our agency, it will cost 20 euro. 
On top of that you will have to add the payment of your Iran Visa to the embassy or consulate.
The amount to pay depends on your nationality.

 To know the current fee you should check with the embassy or check our website

If you wish to do the process of Standard Iran Visa without stress, we recommend you to start 1 months before your arrival to Iran.

Iran Visa allows you to stay for 30 days, but you can extend your Iran Visa in Iran.
All in all, you can hope staying for a maximum duration of 90 days (by chance).

Your Iran Visa will be issued with the validity of 3 months, meaning that once your Iran Visa has been issued, you have 3 months to enter the country.