Fuel injector calculators

Six small tools for the maths that comes up on every injector job — converting flow units, sizing a set for a power goal, checking what a set can support, correcting flow for rail pressure, reading duty cycle from a data log, and sizing the pump that feeds it all. Each calculator prints its formula and assumptions on the page, because a number you cannot check is a number you should not build on.

Injector flow converter — cc/min ↔ lb/hr with the standard gasoline factor. Start here when a flow sheet and a catalogue disagree on units.
Injector size calculator — the flow each injector must deliver for a target horsepower, by cylinder count, aspiration, fuel and duty-cycle ceiling.
Max horsepower from your injectors — the reverse: how much crank power a set you already own can honestly support.
Flow rate at a different fuel pressure — real flow when rail pressure is not the rated pressure, using the square-root rule, in psi or bar.
Injector duty cycle calculator — pulse width and RPM to duty %, with a warning past 85% where metering runs out.
Fuel pump flow requirement — the LPH your engine burns at full power, plus a safety margin for the pump you should actually buy.

How the pieces fit together

A typical sizing session runs in order: size the injectors for the goal, sanity-check the set you are considering with the max-HP tool, correct for your rail pressure, confirm the pump can feed the result, then verify on the road or dyno that logged duty cycle stays at or under 80%. When the car is already together, start from the duty-cycle calculator and work backwards from what the data log says.

Numbers sorted and the car still runs lean or rich? The fault is often mechanical, not mathematical — a clogged micro basket filter quietly strangles flow. Our rebuild guides cover pulling the old filter and servicing the injector; the fitment guide matches service kits to injector part numbers.

Sized them? Now service them

New injectors still need fresh seals and filters. The Universal EV1 Rebuild Kit — 200-Injector Service Tray + Removal Tool, $72.49 covers 200 injectors with matched O-rings, pintle caps and micro basket filters, and the Micro-Filter Basket Removal Tool, from $14.99, pulls the old basket filter without damage.

Free tracked USPS shipping in the US · 30-day returns · secure card checkout by Stripe · sold by Partsapiens.

Shop the 200-injector kit — $72.49 Get the tool — from $14.99

Not sure which kit your injectors take? See kits by injector part number or the fitment guide.

Last updated October 20, 2026 · Partsapiens, 5325 Alton Pkwy, Suite C300, Irvine, CA 92604 · partsapiens@gmail.com