Sildenafil vs tadalafil: speed, duration and cost

Sildenafil and tadalafil are the FDA-approved generic forms of Viagra and Cialis. They work the same way, by blocking the PDE5 enzyme so more blood can flow into the penis when you are aroused, and both worked for most men in their trials. What separates them is timing. Sildenafil peaks in about an hour and covers one occasion. Tadalafil peaks in about 2 hours and improved erections for up to 36 hours after a dose; it can also be taken as a low daily dose.

They also cost about the same as generics: on October 18, 2026, sildenafil cost $1.60 to $6.25 a dose online and as-needed tadalafil $3 to $7.25 a tablet. Here is how they compare on speed, duration, dosing, side effects and what you pay.

Speed and duration

These figures are from each drug’s FDA label.

The sildenafil label says it can be taken anywhere from 30 minutes to 4 hours before sex, and that a high-fat meal slows its absorption by an hour on average. The tadalafil label says it improved erectile function compared with placebo for up to 36 hours after a dose. In one trial of men taking 20 mg, 61% had successful sex 22 to 26 hours later and 64% at 33 to 39 hours, against 37% on placebo at both times.

Neither drug causes an erection by itself. Both need sexual stimulation to work.

Doses

Daily tadalafil is taken at about the same time each day without timing it to sex. The 5 mg daily dose is also approved for symptoms of an enlarged prostate (BPH), alone or with ED. Sildenafil has no daily ED regimen; at a lower dose, as Revatio, it treats pulmonary arterial hypertension. Our sildenafil and tadalafil pages cover dosing in full.

How well they work

The two labels report results differently, so they can’t be compared directly, and no head-to-head trial is reported on either. In sildenafil’s trials of 1,797 men, 63% (25 mg), 74% (50 mg) and 82% (100 mg) reported improved erections, against 24% on placebo. Tadalafil was studied in 22 as-needed trials with more than 4,000 men and three daily-dose trials with 853 men, and it improved erectile function over placebo, including in men with diabetes. If one doesn’t work for you at the right dose, a clinician may suggest the other.

Side effects

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Sildenafil more often causes flushing and brief vision changes, mostly a color tinge or sensitivity to light (3% against 0% on placebo). Tadalafil more often causes back and muscle pain. On daily tadalafil at 2.5 mg and 5 mg, side effects were less common, with headache in 3% and 6% of men against 5% on placebo.

The serious warnings are the same for both. Never take either with nitrates or riociguat, because blood pressure can drop dangerously. Don’t take them together or with another ED drug. Get emergency care for an erection lasting more than 4 hours, and stop and call a clinician for sudden vision or hearing loss.

What each costs online

Generic prices on each provider’s own site, October 18, 2026:

Per dose, sildenafil is usually a little cheaper, especially at 25 mg or 50 mg. Tadalafil’s cost depends on how you take it: occasional 10 mg or 20 mg doses, or 30 low daily doses a month. Strut’s 20 mg tadalafil dose costs $12 because it is four 5 mg tablets, while TRT Nation’s 20 mg tablets work out to about $3.33 each. See where generic sildenafil is cheapest and where generic tadalafil is cheapest for the terms behind each price.

A month of each, side by side

Using the published prices, four occasions a month cost roughly:

• Sildenafil 50 mg at Strut Health: $12.80 of medication, bought as 30 doses for $96 every 90 days.
• Sildenafil at Hims: $16 at $4 a use.
• Tadalafil 10 mg at Strut Health: $24, as part of 10 doses for $60.
• Tadalafil at Rex MD: $24 at its $6 starting price per tablet.
• Daily tadalafil at Hims: from $40 for the month, whatever the number of occasions.

If you have sex a few times a month, either drug as needed is cheaper than a daily plan. If it is most days, or you would rather not plan, daily tadalafil can be worth it.

Which to choose

• Choose sildenafil for planned occasions, the lowest price per dose and a shorter-acting drug.
• Choose tadalafil as needed for a weekend-long window, or if food often delays sildenafil for you.
• Choose daily tadalafil to stop timing pills around sex, or if you also have BPH symptoms.

Compounded chewables of either drug are not generics of Viagra or Cialis and are not FDA-approved; see compounded ED chewables. Our Viagra vs Cialis guide compares the brands and the other two approved pills, vardenafil and avanafil.

The bottom line

Sildenafil works within about an hour and covers one occasion; tadalafil takes about 2 hours to peak but lasts up to 36 hours, and comes as a daily dose. Side effects overlap, with more flushing on sildenafil and more back pain on tadalafil. As of October 2026, both cost a few dollars a dose as generics online. Compare providers in our sildenafil rankings, daily tadalafil rankings or the ED hub.