Corticosteroid Dose Conversion Calculator

Medically reviewed by Dr. Taimoor Asghar, physician.

Convert between hydrocortisone, cortisone, prednisone, prednisolone, methylprednisolone, triamcinolone, dexamethasone, and betamethasone, with each steroid's anti-inflammatory potency, mineralocorticoid activity, and duration of action alongside the number. Use the calculator above, then read the guide below to interpret your result and its limitations.

The equivalence table

Corticosteroid equivalence is conventionally quoted against hydrocortisone 20 mg, the approximate daily physiological cortisol production. The standard equivalents are: cortisone 25 mg, prednisone 5 mg, prednisolone 5 mg, methylprednisolone 4 mg, triamcinolone 4 mg, dexamethasone 0.75 mg, and betamethasone 0.6 mg. These numbers appear in every major formulary, including the British National Formulary, and they are the basis of the conversion formula: new dose equals old dose times (equivalent of new steroid divided by equivalent of old steroid).

A worked example: converting prednisone 40 mg to hydrocortisone. The formula gives 40 times (20 divided by 5), which is 160 mg of hydrocortisone. Converting dexamethasone 6 mg, the RECOVERY trial dose for COVID-19, to prednisone gives 6 times (5 divided by 0.75), which is 40 mg. And methylprednisolone 125 mg, a common intravenous pulse fragment, converts to dexamethasone as 125 times (0.75 divided by 4), about 23.4 mg. The calculator performs this arithmetic for any pair of the eight steroids.

These equivalents describe anti-inflammatory (glucocorticoid) effect only. They are derived from assays of anti-inflammatory potency and clinical experience, not from perfect head-to-head trials for every pair, so they are approximate by nature. Small differences between published tables exist, particularly for betamethasone and triamcinolone, but the values used here are the widely accepted formulary standards.

Potency is not the whole story: mineralocorticoid activity

Glucocorticoids do two jobs: the anti-inflammatory effect you usually want, and the mineralocorticoid effect, salt and water retention with potassium loss, that you sometimes want and sometimes do not. Hydrocortisone and cortisone have full mineralocorticoid activity, which is why hydrocortisone suits adrenal replacement where both effects are needed. Prednisone and prednisolone retain about 80 percent of it, methylprednisolone about half, and triamcinolone, dexamethasone, and betamethasone essentially none.

This matters whenever the indication involves fluid balance. Switching a patient with adrenal insufficiency from hydrocortisone to dexamethasone on pure anti-inflammatory equivalence removes the mineralocorticoid cover, risking salt wasting, hypotension, and hyperkalaemia unless fludrocortisone is added. Conversely, choosing dexamethasone for cerebral oedema deliberately exploits its lack of mineralocorticoid effect: the brain swelling is treated without the fluid retention that would worsen it. The calculator warns whenever a conversion crosses this boundary.

Potassium deserves a mention in its own right. Steroids with mineralocorticoid activity drive potassium out through the kidney, and hypokalaemia is a common, under-monitored consequence of high-dose therapy, especially with hydrocortisone and prednisolone. Patients on diuretics are doubly exposed. Potassium should be checked early in high-dose courses, not discovered via cramps or an arrhythmia.

Duration of action and dosing intervals

Steroids are grouped by duration: short-acting (hydrocortisone, cortisone, 8 to 12 hours), intermediate-acting (prednisone, prednisolone, methylprednisolone, triamcinolone, 12 to 36 hours), and long-acting (dexamethasone, betamethasone, 36 to 72 hours). Duration here means biological half-life, the duration of HPA-axis suppression and anti-inflammatory effect, not the plasma half-life, which is much shorter for all of them.

Duration shapes the dosing schedule. Short-acting hydrocortisone needs two or three daily doses to cover the day, which conveniently mimics the body's own diurnal rhythm in replacement therapy. Intermediate steroids suit once-daily morning dosing, which gives the HPA axis a nightly window and reduces suppression. Long-acting dexamethasone can be given once daily or on alternate days, but its prolonged suppression makes recovery slower when it is stopped.

Switching across duration groups needs more than the equivalent dose. Moving from prednisolone to dexamethasone changes a once-daily rhythm into a drug that lingers for days; moving the other way shortens cover and may need split dosing. The calculator flags duration mismatches so the interval gets reviewed alongside the milligrams.

Adrenal suppression and tapering

Any supraphysiologic steroid dose, roughly above 20 mg hydrocortisone equivalent daily, suppresses the hypothalamic-pituitary-adrenal axis if continued beyond 2 to 3 weeks. The body stops making its own cortisol, and abrupt cessation leaves the patient with no cortisol at all: adrenal crisis with hypotension, hyponatraemia, hyperkalaemia, and collapse. This is why prolonged courses are tapered, not stopped.

Tapering has two phases with different logic. Down to about the physiological level (20 mg hydrocortisone equivalent), the taper is relatively brisk and governed by the underlying disease: the aim is the lowest dose that controls it. Below physiological levels the taper slows right down, often over weeks to months, because now the aim is HPA-axis recovery, and symptoms of steroid withdrawal, fatigue, arthralgia, low mood, can mimic disease relapse. Patients need to know the difference so they do not restart high doses for withdrawal symptoms.

Stress dosing is the companion rule. A patient on prolonged steroids, or recently tapered, cannot mount a cortisol response to major stress: surgery, severe infection, or major trauma needs supplementary hydrocortisone cover per local perioperative guidance. Steroid emergency cards, standard in the UK, exist so that any clinician encountering the patient knows at a glance. Anyone converting or stopping steroids should confirm the patient has one where indicated.

Side effects that scale with dose and duration

Short courses bring the familiar nuisances: insomnia, increased appetite, mood elevation or irritability, fluid retention, and a rise in blood glucose that matters greatly in diabetes. These are dose-related and mostly reversible, but they still need managing: warn the patient, adjust diabetic medication proactively, and consider gastric protection where the risk applies.

Longer courses accumulate the serious harms: weight gain with central distribution, hypertension, diabetes, cataracts, glaucoma, skin thinning and bruising, proximal myopathy, avascular necrosis of bone, and osteoporosis with fragility fractures. Bone protection, calcium, vitamin D, and often a bisphosphonate, should be considered from the start of any course expected to exceed 3 months, per standard guidance, not after the first fracture.

Infection risk rises with dose and duration because steroids suppress immune responses and mask the signs of infection: fever may be blunted while sepsis advances. Live vaccines are contraindicated on significant immunosuppressive doses. And neuropsychiatric effects, from mild agitation to frank steroid psychosis, can appear at any point, more often with higher doses and in susceptible individuals. None of these are captured by the equivalence number, which is why every conversion in the calculator arrives with its profile and warnings attached.

Practical switching scenarios

Asthma and COPD flares typically use prednisolone 40 mg daily for 5 days in adults, a short course needing no taper. If only prednisone is available, the conversion is 1 to 1 at 40 mg. If the patient cannot swallow tablets, intravenous hydrocortisone 100 mg is roughly equivalent per dose, though the mineralocorticoid load is higher, which is acceptable for a day or two.

Cerebral oedema and spinal cord compression use dexamethasone for its potency and lack of fluid retention: a common regimen starts at 10 mg IV then 4 mg every 6 hours. Converting that 16 mg daily dexamethasone to prednisolone would be about 107 mg, an awkward number that shows why dexamethasone is simply the right drug for this job rather than a convertible one. The calculator gives the number, but clinical sense chooses the molecule.

Adrenal replacement uses hydrocortisone 15 to 25 mg daily in two or three divided doses to mimic the diurnal rhythm, plus fludrocortisone 50 to 200 micrograms daily for mineralocorticoid cover. Converting replacement to prednisolone (about 3 to 5 mg daily) is sometimes done for convenience, but the loss of rhythm and the different mineralocorticoid profile make hydrocortisone the standard. In all these scenarios the equivalent dose is the starting point of the decision, never the whole of it.

Sources

• British National Formulary: corticosteroid equivalences (hydrocortisone 20 mg = prednisolone 5 mg = dexamethasone 0.75 mg = betamethasone 0.6 mg). bnf.nice.org.uk
• RECOVERY Collaborative Group. Dexamethasone in hospitalized patients with Covid-19. New England Journal of Medicine. 2021;384:693-704. doi:10.1056/NEJMoa2021436

Frequently asked questions

How do I convert prednisone to hydrocortisone?

Multiply by (20 divided by 5): prednisone 40 mg equals 160 mg of hydrocortisone. The general formula is: new dose equals old dose times (equivalent of the new steroid divided by equivalent of the old steroid), using the standard table where hydrocortisone 20 mg is the reference.

What is 6 mg of dexamethasone in prednisone?

About 40 mg: 6 times (5 divided by 0.75) equals 40. This is the conversion behind the RECOVERY trial COVID-19 regimen, where 6 mg dexamethasone daily was the studied dose and 40 mg prednisolone is the commonly used alternative.

Which steroid has the least salt retention?

Dexamethasone, betamethasone, and triamcinolone have essentially no mineralocorticoid (salt-retaining) activity. Hydrocortisone and cortisone have the most. This is why dexamethasone is preferred for cerebral oedema and hydrocortisone for adrenal replacement.

How long do steroids suppress the adrenal glands?

Supraphysiologic doses (above about 20 mg hydrocortisone equivalent daily) suppress the HPA axis after 2 to 3 weeks of continuous use. Recovery after stopping takes weeks to months, longer with long-acting steroids like dexamethasone, which is why courses are tapered rather than stopped abruptly.

Do I need to taper a 5-day course of prednisolone?

No. Short courses under 2 to 3 weeks can usually stop without tapering because HPA suppression has not established itself. Tapering is for prolonged courses, and the slow phase below physiological levels is about adrenal recovery, not the original disease.

What monitoring do patients on long-term steroids need?

Blood pressure, weight, blood glucose (or HbA1c), potassium, eyes (cataract and glaucoma screening), bone health (calcium, vitamin D, fracture risk assessment with bisphosphonate where indicated), mood and sleep, skin, and infection vigilance. The list is long because the side effects are multisystem: build it into routine review rather than relying on memory.

Clinical sources: British National Formulary (corticosteroid equivalences); RECOVERY Collaborative Group. N Engl J Med. 2021;384:693-704.