Both are PDE5 inhibitors that help you get an erection when you're aroused. The practical difference is timing: Viagra (sildenafil) is usually taken about an hour before sex and works for a few hours; Cialis (tadalafil) is labeled to improve erections for up to 36 hours and also comes as a low daily dose. Generic sildenafil is listed from $2 and generic tadalafil from $8–$11 per dose online.
At a glance
| Viagra (sildenafil) | Cialis (tadalafil) | |
|---|---|---|
| FDA approval (brand) | 1998 | 2003 |
| Usual as-needed starting dose | 50 mg, about 1 hour before sex | 10 mg, before sex |
| Label dose range | 25–100 mg | 5–20 mg |
| When it can be taken | From 30 minutes to 4 hours before sex | Labeled to improve erections up to 36 hours after a dose |
| Daily low-dose option | No | Yes — 2.5–5 mg once a day |
| Food | A high-fat meal can delay it | Not affected by food |
| Maximum frequency | Once a day | Once a day |
| Lowest generic price we found online | $2 (20 mg, Ro) | $8 daily / $11 as-needed (Ro) |
How they work (the short version)
Viagra and Cialis are both PDE5 inhibitors. They don’t create desire and they don’t cause an erection on their own; they make it easier for blood flow to do its job when you’re aroused. The active ingredients are sildenafil (Viagra) and tadalafil (Cialis), and both are now available as FDA-approved generics at a fraction of the brand price.
The real difference: planning vs spontaneity
- Sildenafil is the “plan ahead” option. The label’s usual timing is about 1 hour before sex, and it can be taken anywhere from 30 minutes to 4 hours ahead. A heavy, high-fat meal can slow it down.
- Tadalafil is the “don’t think about it” option. Its label reports improved erections for up to 36 hours after a dose, food doesn’t affect it, and it’s the only one of the two approved as a daily low dose.
If I had to explain it to a friend: sildenafil is for date night, tadalafil is for the weekend. That’s a simplification, and the right choice also depends on your health and other medications, which is your clinician’s call.
What generics cost online right now
From the price lists we track (full table on the price tracker):
- Generic sildenafil: $2 for 20 mg up to $10 for 100 mg at Ro; Hims plans from $22 a month.
- Generic tadalafil: $11 for 5 mg as needed, or $8 for a daily dose, at Ro; Hims plans from $24 a month.
- The brands: Viagra is $90 and Cialis $20–$80 per dose at Ro.
The gap between generic and brand is the biggest saving in this whole category.
Who should not take either
Both labels are clear: never with nitrates (like nitroglycerin for chest pain) or riociguat. Caution applies with alpha-blockers, some heart conditions and some eye conditions. This is exactly what the online visit or your own doctor screens for, so answer those questions honestly.
Where to get them
Every service on this site sells at least one of the two. To compare who charges what, start with Hims vs Ro, or see each provider’s full price list: Ro, Hims, BlueChew.
Frequently asked questions
Which lasts longer, Viagra or Cialis?
Cialis. Its FDA label says tadalafil improved erectile function for up to 36 hours after a dose. Viagra's label describes taking it 30 minutes to 4 hours before sex, with about 1 hour as the usual timing.
Is generic Viagra the same as Viagra?
Generic sildenafil has the same active ingredient as Viagra and is FDA-approved. Online, generic sildenafil is listed from $2 for a 20 mg dose at Ro, while branded Viagra is $90.
Can you take Cialis every day?
Yes, tadalafil is FDA-approved as a once-daily low dose (2.5 mg, up to 5 mg) for ED, taken at about the same time each day regardless of when you have sex. Whether that suits you is a question for your clinician.
Can I take Viagra or Cialis with nitrates?
No. Both labels contraindicate use with nitrates (such as nitroglycerin) because the combination can cause a dangerous drop in blood pressure.
What are the common side effects?
The labels list headache, flushing, indigestion, nasal congestion and back or muscle aches among the most common side effects for both drugs. Sildenafil can also cause temporary changes in vision, such as a blue tinge.