Trial Duration Estimator
ANA›Life Services Authority›National Calculator Authority›Trial Duration Estimator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Trial Duration Estimator
Estimates the total duration of a clinical trial based on enrollment parameters, required sample size, follow-up period, and expected dropout rate.
Required Sample Size (participants)
Monthly Enrollment Rate (participants/month)
Expected Dropout Rate (%)
Follow-up Period per Participant (months)
Trial Startup Period (months)
Closeout Period (months)
Calculate
function triCalc() { const errEl = document.getElementById('tri-error'); const resEl = document.getElementById('tri-result'); errEl.style.display = 'none'; resEl.style.display = 'none';
const n = parseFloat(document.getElementById('tri-sample-size').value); const rate = parseFloat(document.getElementById('tri-enrollment-rate').value); const dropout = parseFloat(document.getElementById('tri-dropout-rate').value); const followup = parseFloat(document.getElementById('tri-followup').value); const startup = parseFloat(document.getElementById('tri-startup').value); const closeout = parseFloat(document.getElementById('tri-closeout').value);
// --- Validation --- if (isNaN(n) || n 0).'; errEl.style.display = 'block'; return; } if (isNaN(rate) || rate 0).'; errEl.style.display = 'block'; return; } if (isNaN(dropout) || dropout = 100) { errEl.textContent = 'Dropout rate must be between 0 and 99%.'; errEl.style.display = 'block'; return; } if (isNaN(followup) || followup ' + 'Adjusted Sample Size (with dropout)' + '' + nAdjusted.toFixed(1) + ' participants' + 'Enrollment Duration' + '' + tEnrollment.toFixed(2) + ' months' + 'Startup Period' + '' + startup.toFixed(2) + ' months' + 'Follow-up Period' + '' + followup.toFixed(2) + ' months' + 'Closeout Period' + '' + closeout.toFixed(2) + ' months' + 'Estimated Total Trial Duration' + '' + tTotal.toFixed(2) + ' months (' + tTotalYears.toFixed(2) + ' years)' + ''; resEl.style.display = 'block'; }
#### Formula
Step 1 — Adjusted Sample Size:
nadjusted = n / (1 − dropout_rate)
Step 2 — Enrollment Duration:
Tenrollment = nadjusted / enrollment_rate
Step 3 — Total Trial Duration:
Ttotal = Tstartup + Tenrollment + Tfollow-up + Tcloseout
Where all time units are in months.
#### Assumptions & References
- Enrollment rate is assumed to be constant throughout the enrollment period.
- Dropout is assumed to be uniformly distributed across participants; the sample size is inflated upfront to compensate.
- Formula based on standard clinical trial planning methodology: Friedman, Furberg & DeMets — Fundamentals of Clinical Trials, 5th ed.
- For multi-site trials, the effective enrollment rate should be the sum of all site-level rates.
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