Engine TBO Remaining Calculator
Hours and months to TBO from current engine time — with the calendar limit that quietly overtakes low-utilisation engines.
TBO has two clocks — hours AND calendar (typically 12 years) — and the calendar one wins on most privately flown engines.
Check the engine maker's calendar TBO too (commonly 12 years): a 600-hour, 14-year engine is past TBO on age. Part 91 may run on condition; budget as if the date is real.
With your numbers: At 1,340 h SMOH against a 2,000 h TBO, 660 h remain — roughly 55 months at 12 h/month (67% consumed).
⚠️ Not for operational decisions. This is a record-keeping and planning aid only — not certified avionics, not a source of regulatory truth. Always verify against official sources (FAA) and your operator's approved documents before flying.
Free TBO calculator: hours to overhaul, months at your utilisation, and percent consumed — plus the 12-year calendar limit reminder that low-time engines ignore at their wallet's peril.
About Engine TBO Remaining Calculator
TBO planning is the largest single line in piston ownership economics: a four-cylinder overhaul runs well into five figures and the six-cylinder turbocharged kind far beyond. This calculator gives the planning numbers — hours remaining, months at your actual utilisation, percentage consumed — so the reserve fund and the overhaul conversation both start years out. Two truths worth internalising: Part 91 operators may legally run past TBO on condition (oil analysis, compressions, borescope trends all healthy), and the calendar TBO most makers also publish (commonly 12 years) overtakes the hour limit on most privately flown engines. The cheapest overhaul is the scheduled one; the expensive one follows a metal-making oil sample on a holiday weekend.
How to use Engine TBO Remaining Calculator
- 1Enter hours since overhaul, the published TBO, and monthly utilisation.
- 2Read hours and months remaining; set or check your hourly overhaul reserve.
- 3Past 80% consumed, tighten condition monitoring and start shop conversations.
Why use Engine TBO Remaining Calculator?
- ✓Hours, months and percent-consumed in one computation
- ✓Utilisation-based month estimate makes the reserve math concrete
- ✓Flags the calendar-TBO trap for low-utilisation engines
- ✓Frames the on-condition decision with honest numbers
- ✓Instant, free, browser-only
Frequently asked questions
Can I legally fly past TBO?+
Under Part 91, yes — TBO is the manufacturer's recommendation, not regulation, and many engines run safely beyond it ON CONDITION: stable oil analysis, healthy compressions and borescope findings, no metal in the filter. For-hire and many 135 contexts are stricter. The honest framing: past TBO you're spending the engine's margin, so the monitoring that justifies each additional hour becomes the real maintenance program.
How much should I reserve per hour for overhaul?+
Divide a current overhaul quote (call your preferred shop — prices have moved sharply) by the hours remaining to TBO. A $42,000 overhaul with 1,400 hours remaining is $30/hour into the reserve, on top of fuel and routine maintenance. Owners who run this number annually are unsurprised at overhaul time; the percentage-consumed output here exists to prompt exactly that annual re-check.
Hours TBO or calendar TBO — which will I hit first?+
Divide the hour figure by your honest annual utilisation: at 100 hours/year a 2,000-hour TBO is twenty years away, but the 12-year calendar limit arrives at year twelve regardless. Most owner-flown engines are calendar-bound, which reframes decisions: an engine at 900 SMOH and 11 years isn't 'halfway to overhaul' — it's a year from the conversation.
Is this tool private — who can see my entries?+
Only you. Entries live in your browser's local storage and never leave your device, so there is no account, no cloud sync and no one else with access. Because the data is device-local, export a CSV backup before clearing browser data or switching computers.
How do I back up or print these records?+
Use the Export CSV button below the table: it downloads your full overhaul plan as a spreadsheet-ready file. From there you can print a clean copy, archive it with your records folder, or import it into any other system. Exporting monthly is a good habit since the working data lives only in your browser.
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