Calculate drive train efficiency
Overall efficiency across up to four stages, power loss, reverse efficiency with the self-locking limit — optionally with annual energy, energy cost and a comparison against a second variant.
Calculate drive train efficiency
Enter the stages and the power — results appear immediately.
Stages of the train
Operation
Without operating hours the energy section stays hidden.
Formulas
η_ges = η₁ · η₂ · … · ηₙ P_an = P_ab / η_ges P_V = P_an − P_ab η′ ≈ 2 − 1/η_ges W = P_an · t ΔW = P_ab · (1/η_A − 1/η_B) · t t_Amort = Mehrpreis / (ΔW · Strompreis)
The preset per type is the lower end of the range given in the guide — deliberately conservative. Every value can be overwritten.
What the model covers
The calculation uses a fixed efficiency per stage. In reality it depends on load, speed, oil temperature and viscosity: under part load the load-independent losses stay constant, their relative share grows, and the efficiency drops below the catalogue value (ISO/TR 14179). The calculator uses the value you give it — it does not check whether that value holds for your operating point. Toothed belts and chains are not offered because no documented values are available; enter your catalogue value via “Own value”.
How the overall efficiency comes about
The efficiency of a single stage is the ratio of output to input power: η = P_out / P_in. With several stages the individual efficiencies multiply — they do not average. Two planetary stages at 96 % and 95 % therefore give not 95.5 % but 0.96 · 0.95 = 91.2 %. That is exactly why every additional stage costs more than it appears to at first glance.
From the overall efficiency follows the input power to be provided, P_in = P_out / η_total, and the difference P_loss = P_in − P_out goes into the housing as heat. At 7.5 kW input power and 91.2 % that is 660 W to be dissipated — which decides housing size, cooling fins and, in case of doubt, forced cooling.
The preset per type comes from the table in our guide Calculating gearbox efficiency and is always the lower end of the range given there. That is deliberate: a calculator that silently assumes the best case shows too little power loss and too short a payback — both in the direction that works against you. Every value can be overwritten once you have the catalogue figure for your gearbox.
Reverse efficiency and the 50 % limit
When a gearbox is driven backwards from the output side, the reverse efficiency η′ applies, and it is always lower than η. It can be approximated from the forward value: η′ ≈ 2 − 1/η. Substituting η = 0.5 gives η′ = 0 — the theoretical limit of static self-locking. The calculator applies the approximation to the overall efficiency and treats the limit as inclusive: exactly 50 % already counts as self-locking.
One caveat: this statement holds for a load at rest. Under vibration or shock the effective friction drops, so a nominally self-locking gearbox can still creep back. For safety-related holding functions, self-locking is therefore no substitute for a brake.
Frequently asked questions
Why are toothed belts and chains not offered?
Because we have no documented figure for them. The table the presets come from lists only “belt drive (standard)”, which means the V-belt. Toothed belts and chains sit above that, but a number from gut feeling is the wrong tool in a sizing calculator. Choose “Own value” and enter the figure from your catalogue.
Does the catalogue efficiency also apply under part load?
No. The catalogue value applies at the rated operating point. The load-independent losses — churning, seal and bearing base friction — stay almost constant at a given speed while the transmitted power falls. Their relative share therefore grows and the efficiency drops. With worm gearboxes the effect is strong enough that they can fall below the self-locking limit under part load. ISO/TR 14179 covers how the losses are split.
How reliable is the payback figure?
Exactly as reliable as your three assumptions: additional cost, electricity price and annual running time. The calculation takes them as given and computes ΔW = P_out · (1/η_A − 1/η_B) · t. It is an order-of-magnitude comparison of two variants, not an investment appraisal — maintenance, downtime risk and spare-part availability are entirely absent from it. For those, the framework is in our guide on TCO in the drive train.
Does the calculator say whether the gearbox will cope thermally?
No. It gives the power loss that arises as heat — not whether the housing can dissipate it. The thermal continuous power limit follows from the heat balance of the specific gearbox and is given in the manufacturer's curves. Send us your values and we will check it together with the mechanical sizing.
Note: The calculation tools provided are intended for initial orientation only and do not replace a binding design by qualified engineers. All results must be verified by appropriate engineering calculations before use in safety-related applications. Technische Antriebselemente GmbH accepts no liability for damage arising from the use of the calculation results.
Have a gearbox sized for the required output power?
Overall efficiency and power loss are settled — what remains open is the heat balance in the housing, the efficiency at the actual operating point and whether the ratio can be spread over fewer stages. Carry your values into the enquiry and we will propose matching gearboxes from our range.
Related products & guides
Calculating gearbox efficiency
The source of every formula and table value in this calculator — with loss types, part-load behaviour and worked examples.
GuideSelf-locking: when is it wanted?
Why the 50 % limit applies to a load at rest and where a brake still belongs.
ComparisonWorm vs. planetary gearbox
The comparison behind the payback calculation: efficiency, installation space, cost.
ProductWorm gearboxes
High ratio in a single stage, right-angle drive, self-locking depending on the lead angle.
ProductSpiral bevel gearboxes BG
The same right-angle drive as the worm gearbox, but at considerably higher efficiency.
CalculatorGearbox Ratio Calculator
The quantity this calculator presupposes: the ratio and the output speed.